Hi Kim!
I can absolutely understand where you're coming from. My daughter is an extremely picky eater as well. Luckily, most restaurants have the usual kid favorites like chicken nuggets, pizza, hot dogs and peanut butter and jelly.
I feel that the buffet meals at Disney truly offer a large variety of foods and are usually more economical than other table service restaurants. At the Magic Kingdom for table service I would recommend the
Crystal Palace. This buffet restaurant is open for breakfast, lunch and dinner. It also has the added bonus of being a character meal hosted by Winnie the Pooh and his friends. The food selection for all meals is wonderful. There is a children's section of the buffet, but kids are welcome to any of the items.
If you're looking for a good quick service restaurant at the Magic Kingdom with a big variety of food then I would suggest Cosmic Ray's. There are several different "bays" here that all offer different items. Some of the offerings include bbq chicken, turkey wraps, soups and burgers just to name a few. When you enter ask a cast member for a menu that will show you what items are being served in each bay to help you make your choices.
At Hollywood Studios you can find a table service buffet for all three meals at
Hollywood & Vine. Breakfast and lunch here are character meals. For picky eaters you might want to visit Pizza Planet where they give you the option of combo meals including salad and pizza.
Unfortunately, you can not get the dining plan if you aren't staying at a Disney resort so it's very important to get an idea of where you will be eating while on vacation so that you can budget accordingly.
I hope this helps! Have a fantastic vacation!