Howdy neighbor.
When planning on a budget, remember that all of the lunch prices are cheaper than the dinner prices - usually by $8-10 per person.
Biergarten in Epcot is a lot of fun, and while I don't remember chicken nuggets as such, there are things that are not terribly exotic. The kids (then-5 & 18months) we had with us last time we were there with kids they found plenty to eat - mac and cheese, spaetzle, roast chicken, frankfurters, potato salad.
One of my personal favorites is Crystal Palace. This one includes characters, but the food is very good and there is nothing like having lunch with a view of the castle. Food quality-wise, I would put this one in front of Biergarten.
Tusker House in the Animal Kingdom is very reasonably priced, and has pretty good food. Their buffet is a bit more exotic (African and Middle-Eastern influences on much of it), but they do still have the ubiquitous chicken and potatoes, so picky eaters won't starve.
The best value for money is Trail's End at Fort Wilderness (a boat takes you there from the Magic Kingdom). Simple - fried chicken, mashed potatoes, veggies, barbecue, salads, sometimes pasta - but the dinner buffet here has the same cost as most lunch buffets (it was $23 for adults in September). We like to go and then follow dinner with the (free) campfire movie with Chip and Dale.
HTH!
