We've made many trips where we had most of our meals "in". My favorite tip is, if time allows, do as much pre-prep as you can on arrival day. If we flew I would hit the grocery and then do things like cook a huge pot of pasta and brown some ground turkey/beef. We used the pasta for both dinner at the camper and the pasta salads that we sometimes carried into the park. The ground meat went into pasta sauce and tacos. Throw some b/s chicken breast in the oven to use for salads or other quick meals. I was big on entree salads-they're easy to pull together, customizable and nice after a hot day in the parks. By doing most of the dirty work right away it was fairly simple to throw dinner together in the evening. I also highly recommend lining baking sheets with foil and using paper plates to help with the cleanup.
If you have the luggage space you can pull a lot of your non-perishables from your pantry. I've brought pasta, rice, crackers, bread, trail mix etc. I would also bring things like homemade muffins and snacks in my carry on. Seasonings are my #1 staple to bring from home since it can get pricey buying whole packages of each thing you'll need. I bring salt, pepper, taco seasoning, Cajun seasoning, garlic ect. transferred from the bulk containers in my freezer into smaller containers. I'm a pretty frugal shopper at home and utilizing stuff (bought on sale, often with a coupon) from the pantry stock frees up funds that can then be used for the fun stuff.
We took our kids' friends to WDW several times and I almost always asked them to bring along a few of their favorite pre-packaged snacks to fill the gaps between meals. We still had the occasional Mickey ice cream but the snacks REALLY came in handy when the teen-aged hunger pangs kicked in. By bringing their own each kid had something I knew they liked.
We were usually camping at Ft Wilderness which made going back for lunch or dinner easy but we also sometimes took picnics in. I know it's not for everyone but I would pack wraps, pasta salad, veggie sticks/hummus, etc to eat while we waited for Fantasmic, Illuminations or a parade.
I would also wait to add the hopper and WPF&M. It's been a while but I believe a single admission to one of the water parks is less expensive than the add-on and you may not have time to go more than once, or it could monsoon or you may find that you just don't feel like it.
Happy Planning!