We went earlier this year and stayed at the all star movie resort, it is a budget resort and was not bad, you are not going to spend much time at your resort anyway. My wife and I went before we had kids and stayed at Animal Kingdom Lodge, that was very nice, but I dont think kids would appreciate it for major cost difference. We shipped a package to our hotel from us with cereal, fruitsnack, 2 loafs of bread penutbutter, jelly, vodka, ect. Then we bought 1/2 gallon of milk at the resort, that way we were able to make breakfast in out room and bring our own snacks into the park. We were also able to NOT buy the meal package. We bought it the first time we were there and still had meals available when we left.
As far as cost It is going to vary alot based on were you stay and what you do while your there.