Other than a few treats that we have at home (organic home made popsicles, organic fruit strips, organic cookies, etc.) we leave the "junk food" out of our house. We let that be a treat to have when they are visiting friends or relatives or when we are on vacation.
I totally think it is okay to give them sweets once in awhile. Like right now we have Spiderman fruit snacks in our house because they were on sale for $1 a box. I usually don't buy these. So if DS who is 3 eats his dinner like a big boy, he gets a bag or two of these as a treat.
And about once a month we do a family icecream run where we walk to Target and each get a scoop of icecream.
But at age 8 months, we really limited the amount of sweets our kids ate. A few bites or licks here and there is okay. And some watered down juice was about all they got. Once they turned 1, we got a little more lenient, but we still limit the amount of sweets and junk food they get. I would say that compared to the junk that I see their friends eat, my kids get about 1/4 of that.
Good for you for keeping your kids healthy.
As for going all vegetarian, it's definitely a good idea to eat more fruits and veggies. But do your homework on the downfalls of vegetarianism. There are a few proteins and other nutrients that you need from dairy and meat, etc. Right now I consider our family to be semi vegetarian and semi meat eaters. We eat red meat about twice a week, poultry twice a week, soy twice a week, and all veggie once or twice a week. I usually cook a large dinner and then we eat the left overs for lunch the next day. As I am sure you have heard many times before, variety is best. Even at 8 months you can incorporate a variety of foods into your daughters diet. For both my kids we alternated between organic jar foods and just steaming the foods that we were eating for meals for them. And since we are a mixed race family (German, Irish, Norwegian, English, Japanese, Korean, Cambodian, and Black) we always have a variety of things to eat. I.e. my 3 yo son is now eating nori (Japanese seaweed strips) as a snack. And both of my kids (age 3 and 1) LOVE to eat sushi. I will go bankrupt if I take them to eat Japanese food as much as they would like.
Have fun introducing all the flavors of food to your little girl. And don't worry about giving her a little sweet every so often. Trust me by the time she is 2 she will be nagging you for it ALL the time! They learn really fast that the other kids around them are getting the junk food. So take advantage of the fact that right now she is too young to no otherwise and will eat anything you put in front of her.