If you are not big eaters, start by sharing a meal. Then if you're still hungry you can go back for more, or go experience another place. But if you get a meal for everyone and find out you're over-full, you can't send food back for a refund!
Also check out the kid's meals. I've only gotten them at counter service places, and they were the bean and cheese burrito meals at Rancho and Cocina Cucamonga, and also the penne pasta meal at Plaza Inn, but they are GREAT. Very filling, very good, and they include a drink (you have to ask if you want a little cup for soda, but I just generally get the little bottle of water).
We had dinner from Millie's. Hubby and I and our *starving* 4 year old (he gets so excited in the parks he forgets that he's hungry and refuses to eat) had ONE macaroni and cheese entree with ONE salad and ONE garlic bread order. It filled up all of us! And was only something like $11. We got it to go on our walk back to HoJos and it was still hot when we got to the room. So good.
There's also Coco's on Katella.