I'm not sure you'll be happy with the choice to go back to the hotel for dinner every night. You'll have to leave the parks early, which will not be a happy thing with kids the ages of yours. If you're traveling in the summer (so that the parks are open late-late), you'll have the option of coming back after dinner; however, that's wasted time. Even if your hotel is "right next to" Disney World, you're going to have an hour's transit time each way (including to the parking lot, etc.).
What are you going to save by going back to the hotel? Remember you're still paying for two adult meals. You're probably going to save $10-12 per dinner. How much did your hopper passes cost? Figure out per hour how much it's costing you to leave the parks for dinner.
If you're looking at fast food in the parks, you can use the same money-saving strategies that work at lunch time:
Someone else already suggested splitting a meal -- a great idea. A double burger is about a dollar more than a single burger; yet it can feed two people. Chicken nuggets are easy to split.
If half a meal doesn't fill your kids up, tell them it's a "hold you over" snack until you get back to the hotel. Bring a big cooler full of snacks, sandwich materials, etc. Bringing from home is always cheaper than buying prepared food anywhere.
Order a double burger AND a plain bun for an additional fifty cents. You can figure out what to do from there!
Cosmic Ray's (?) offers a $15 family meal. It's chicken and the fixings. That's probably about the same amount you'd spend to feed two adults at the Holiday Inn.
Sodas for four will add about $8 to your bill. Ask for FREE ice water (also a healthful choice) and save quite a bit.
If you're relying heavily on fast food places, you may get tired of burgers. Epcot fast food has many other choices.
Order kids' meals, which are plenty big for all but the most ravenous. They're much less expensive. You could probably feed the whole family for less than twenty dollars.
Snacks can kill your budget quicker than meals. Bring plenty of snacks that can fit into fanny packs, and explain to the kids that these snacks are free but THEY must pay for all snacks bought at the park. If they're like my kids, they'd rather have a tee shirt than a bag of popcorn.