Hi Sallie!
I can definitely help you because I just went through the same debate myself for an upcoming trip. I absolutely love all the Walt Disney World (WDW) resorts, but my two favorites are Polynesian and Beach Club Resort.
What helped me decide was comparing the best features at each resort, and then deciding what was most important to me.
Polynesian is wonderful because the restaurants are great ('Ohana) and you can even get a Dole Whip at Polynesian in Pineapple Lanai. You can also enjoy the Spirit of Aloha show. Polynesian also has a beach which offers the absolute best view of Wishes. At the Polynesian you are also on the monorail line for Magic Kingdom at Epcot.
The Beach Club Resort feels like a luxurious beach vacation. The pool has sand at the bottom, which is a completely unique experience. You are also close to Epcot and can walk there through the International Gateway. However, you will have to take a bus transportation to Magic Kingdom, Animal Kingdom and Hollywood Studios. You are on the Boardwalk so you will enjoy nightly entertainment. You also have quite the nightlife options available at this location, with Jellyrolls and the
ESPN Wide World of Sports Grill. You will also be close to Beaches & Cream, which has the famous Kitchen Sink Sundae.
Since your youngest is 18, The Beach Club Resort might be a good option for your family. There is plenty of entertainment, delicious food and options for things to do at night.
I hope you have a magical vacation!
Magically,
Stacy