You know you and dh can split a larger meal such as at Rancho del Zocalo, even though it's Mexican, I don't consider it spicy, really. They have the enchilada platter and the 1/2 chicken that you, dh and a lighter eating child could split. You can split snacks if you bring baggies: cotton candy, popcorn, candies. Lollipops from the Candy Palace are great cheap snacks and last a looong time.
I totally agree with a PP, that the kids' meals are so pathetically small, we don't even bother with them.
Your family may not always be hungry for a big meal. Hot dogs are around $6, or just a Mickey pretzel for around $3 and split a bag of grapes. We do that sometimes and that's a cheap meal. Bring in Crystal Light packets to flavor a free water.
There's a lot you can make in a microwave and eat back at the hotel. If they have picnic tables or a dining area, you don't have to worry about messing up the room, and you could make all kinds of things like chili dogs, nachos, tacos, quesadillas, or get a rotisserie chicken from the grocery store, a bag of microwave rice, steamer micrwave veggies and a bag of rolls for dinner. Somewhat nearby there is Costco for the infamous $10 pizza and Pizza Hut too.