J.L.
What you describe happens to alot of homeschoolers at one point or another. It's tough when you're the teacher but you don't get to leave your work behind when the day is over! LOL!
Anyhoo, I sense you are beating yourself up over things that really are not that big of a deal, that is if you don't let them become a big deal. I think you all need a change of scenery and perhaps routine on a day to day basis. Sounds to me like none of you have enough opportunities away from each other during the week.
If you haven't already, find a homeschool co-op or support group. That alone will help with the monotony. Hopefully, the group will host regular, age appropriate activities for the kids to participate in so that they're not constantly together all of the time. If it's a support group, even you, the mom will have opportunities to hang out with other homeschooling moms, which is very nice because you can glean ideas on how to organize the house, or vent and realize that the craziness you experience isn't so unusual. To find one in your area, go to www.hslda.org and look up your state in the "You can Homeschool" section and you'll be able to find homeschool organizations listed through HSLDA.
If there are no opportunities like this in your area, or you are in a co-op/support group but it isn't cutting it for you and your family, or your or your children's disabilities prevents you from joining a group like this, I suggest finding something non-homeschool related that affords you all chances to be away for a while with your own kind. :)
I really think the kids fussing and fighting is more about their gender and interests, than the fact that they are so close in age. They're at that age where it's important to be with just the girls or just the guys. I don't know too many boys and girls between the ages of 7-12 that want to hang with each other...even if they're siblings. It's bound to be a recipe for wackiness.
Perhaps your daughter would enjoy some female companionship with girls her own age by joining a library book club, dance class, or arts and crafts program? And your son would enjoy open gym, Scouts, or some type of activity through community ed. that gives him an opportunity to burn some of that boy energy with other boys his age. If the disabilities you mentioned are a factor in choosing activities, perhaps you can contact an organization in your area that helps kids with challenges find social outlets. We have some organizations like that here such as Pacer Center and the Courage Center. I'm certain there is something similar in your area. I'd start there and see what you find. Whatever you do, I think getting each child out of the house, away from each other for at least once a week will make a tremendous difference for you at home, and it will give you time to do something one-on-one with the child who is still at home.
As for schooling and keeping peace. Do you sit in the same room to work at the same table? I don't know how your home is set up, but if it's big enough, it may be time to set up work stations in different places in the home so the kids are separated and unable to distract or interact with each other during lessons.
If your home is small, it may be time for you to sit between them at a shared table to ensure no Tom Foolery is going on. I know some moms who will use the time their kids are supposed to be quietly reading or working on papers to clean the house and get the day to day things done. But sometimes this isn't possible if the kids are really young and haven't learned to self regulate and stay on task. They need to see you sitting there to stay on task. If you have to do this, get a timer and set it for blocks of time. Tell the kids they need to work within that window of time and finish their current class/project/paper or they won't be able to take a break at the end of the time. In between lessons, have physical activities planned to jump start their brains and work out the ants. There is a great article today at http://thepioneerwoman.com/homeschooling/ in the homeschool section about the need for homeschoolers to incorporate physical activities throughout the day. It is so easy to get into this thing where your kids are practically chained to the chair working and they get antsy, crabby and sometimes down right crazy because they don't have enough outlets to burn energy. The author gives some very creative ideas to keep things happy and busy at home. Some other great resources include books by Carol Barnier and Melissa Boring:
Here's a recent homeschool lecture short by Carol Barnier. She homeschools a special needs child. She's inspiring:
http://www.youtube.com/watch?v=geI_S6oe9sU
http://www.youtube.com/watch?v=OLoVt1JXpCs&feature=re...
Here are books.
http://www.amazon.com/Big-What-Book-Learning-Styles/dp/19...
http://www.amazon.com/How-Your-Child-Refrigerator-Learnin...
http://www.amazon.com/Diapering-Watermelon-Then-Whered-Le...
They both have blogs as well:
www.sizzlebop.com
www.headsupnow.com
You'll like Dianne Craft as well:
As for keeping the house cleaned an organized, I don't know too many homeschoolers who have perfect homes. You have to remember, you are home all day and the home is being well used! You probably have lots of books and papers to manage and who knows what type of space you have to work with? If possible, take a few days to get the home organized to suit your day to day needs. The goal should be to create a home for everything you use daily. For the rest, consider whether you need to keep it at all and either toss it or donate it.
During the day, take breaks just to make everyone straighten the area up and get it neat again. If the kids are old enough to work in the kitchen, have them make their own breakfasts, snacks, and take turns with lunch duty. Invest in microwave cooking dishes so the kids can safely cook. Convection or counter top toaster ovens are great too. This opens more time for you to get other things done. They can each take turns loading the dishwasher or washing dishes and putting them away. A great breaktime activity can be a relay to see which kid can finish a house task first. One can load and empty the washer and dryer and the other vacuum a room. The first one done gets a small candy treat. Or they can have a clothes folding relay the winner gets an extra five minute break before hitting the books again. For dinners, you can load up a crock pot first thing in the morning, and by the time hubby is home from work, dinner will be ready and fuss free. Just get creative and you will see things will get done. Don't be afraid to have the kids be part of the solution.
Last, but not least, if you don't find a homeschool support group, you yourself should still find something you enjoy doing that is outside the home. A little as one hour away each week can do wonders for recharging your soul. Take a knitting class, learn Kung Fu, or join a church organization or just go to church. Being surrounded by quiet and stained glass can be as theraputic as going to a spa! And it doesn't cost money. :) You might be able to take a community ed. class while your children are busy at a class, cutting down on a need to worry about daycare or travel issues.
Finding a homeschool chat room or message board like this is a great help too. When you need to vent or some instant support you can get it. Check out http://homeschoolcentral.com/message.htm
This is a great place to start, you'll find there are so many forums and message boards to join!
Stay strong and positive. This phase shall pass. It is only a phase. You aren't alone and you aren't doing anything wrong. You just may need to change things up and get out more. It will all work out. You'll see. HOpe this helps some.