Hi Eric,
You are going to have a great time taking your girls to Walt Disney World for the first time! It truly is a magical place where parents and children can have fun together.
There are so many fun resorts, you'll need to ask yourself a couple of questions. Where do you envision spending the majority of your time? What is your budget? There are great resorts at a variety of price points. Art of Animation and Pop Century are both really fun resorts that I think your daughters would love. My only downside to these resorts would be transportation, the buses can get really crowded at times. Although it's more of an issue when traveling with small children who need to be held.
If you're looking for a moderate priced resort, I think your girls would love the
Royal Guest Rooms at Port Orleans. They are gorgeous, and Port Orleans is a fun resort with a great pool area.
My personal favorite would be Yacht or Beach Club Resort. These two resorts are located on the Boardwalk within walking distance of both Epcot and Hollywood Studios. It doesn't get much more convenient than that! The pool area is like a mini water park with a slide, sandy bottom, and even a lazy river.
If your girls love animals, and you want to go all out. Animal Kingdom Lodge is fabulous. There's nothing quite like having a savannah room and waking up with zebra and giraffes outside your window.
As far as the dining plan being a good value. It depends. If you are typically big eaters, then I would say, yes, you can definitely get your money's worth. I like the regular dining plan best, because you can enjoy character meals and some of the unique dining at WDW. The best part of the dining plan for me is that things are already paid for, so you can just sit back and relax on vacation.
Hope this helps. Have a magical vacation!