L.:
We were there with our 3 kids (ages 12, 10 & 5) at Thanksgiving. It was crowded but one of the things that made it easier was getting into the parks as soon as they opened - this way you get maximum ride time before it gets too busy. Also. stick to one park a day. The cool thing about disney is that even when you are waiting or in the time going from one attraction to the next, there is always something else to see and do. Give your girls a spending budget (worked like a charm for mine) or you will be eating bologna sandwiches for the next month. As far as other meals goes, there are lots of self serve places in the parks so you do not need to worry about making reservations. This food is not cheap but some of it is not half bad. If there is a particular restaurant you do want to go to, try making a lunch reservation - should be easier.
Don't know if you have princess obsession in your house but if so, the princess lunch at Akershes (sp.) in the Norway pavillion in Epcot was wonderful (you can try to get a reservation). And my daughter was over the moon about her princess make over at the Bibbity, Bobbity boutique - what a great experience for her. Buy your girls autgraph books as soon as you get into the park and get a schedule of character appearances - it is very easy and a major thrill to see the characters.
One last thing, fast pass is excellent. Check the website to see how it works but it really helps with the line time.
Have fun and remember that this is not a relaxing trip. You'll make lovely memories but it is exhausting!
R.