Oh yes, I went through the same thing! My son started Kindergarten this past Aug and I starting crying 2 weeks prior to him starting. I am a stay at home mom as well and very protective. I worry about him not being old enough to take on such a huge step, I worry about him needing me and not being attended to as I do to him, etc The way that I got passed it was sitting down with him while my 3 yr old slept. I spent as much alone time with him as I could. I cried to him, I told him that I was going to miss him so much. I asked him if there was anything that scared him and if there was anything he wanted to do before he started school. He hugged me and told me that he is a big boy and is excited to start school. This was the first time he has ever not cried when he saw me cry. That made me realize that he really is excited and that he really is growing up. I had to change my way of thinking from "this is the end of him being my baby boy" to "we are moving on to another phase of life and it is all exciting". It made it a bit easier knowing that I still have my daughter who is 3 and I still hvae a "baby" at home. Each day is exciting and just know that there are several phases that they will go through, each phase is more exciting thant he last. It reminded me of when our son was born. When he sat up for the first time, he ate solid foods, he rolled over, he walked, he talked, etc I would get sad b/c he was not a newborn anymore, but then I would think that each phase is so exciting!!! Get a tub/bin to keep all of her new projects and things that she makes in it. Get a journal to document all of the exciting things, your thoughts, her comments, etc Take pictures of her first day, take her shopping for a new backpack, lunch box, etc Take her to lunch, a movie, etc just the three of you. Get a sitter for your younger son and spend the day with just your daughter. Let her choose where you eat and what movie you see. Or go bowling, mini golf, etc Make the month prior to her first day all about her. Lastly, do NOT start worrying so soon. AT least wait until a month before to worry. Just make sure she is prepared and it will be a lot easier for you and your husband. Keep that family cocoon, we feel the same way. As long as we have us four, life is great. We are a very close family and spend a lot of time together. Eat dinner together nightly, play games, sit and just talk to your kids and you will start to feel better about it. It is just the next phase. Oh, and, you WILL find that you enjoy your time while she is at school. Even if you think that you won't, you will. It really is a nice way for you to have time to get things done, time alone with your younger son that your daughter had with you. I always felt like my son got more alone time with me b/c his sister wasn't born until he was 2 1/2 but now, I look at it like this is her time to be alone with me while he is at school. It all works out.
I would also consider driving her to school b/c the bus was a HUGE fear of mine. Also, be very involved in the school and you will know that she is being taken care of. I am always involved in the parties, the teacher's luncheon's, etc Keep in touch with the teacher through notes or email, volunteer in her class if you are able. You will feel much better being involved and knowing that she is being taken care of. You can also eat lunch with her whenever you want to, you can do that once a week with your son if you want to. Think about putting your son in a preschool so he can get the social skills he needs to be prepared for school and then it will give you a day or two a week to be more involved in your daughter's school. Also having him at preschool or mother's day out will help you let go when it is his turn to go to school.
:o) W.