The one that has the most "magic" for your family...They're all great resorts. Choosing the perfect one for you is hard for anyone else to suggest.
If you usually have a car, Old Key West and Saratoga Springs are large and spread-out, but you can park near your building.
If you're going to rely on WDW transportation exclusively, they all have good access to get you just about anywhere on WDW using the buses, boats, and monorail trains. (None of the
DVC resorts aredirectly on the monorail lines at this time.)
Wilderness Lodge is located closer to the Magic Kingdom.
Beach Club and Boardwalk are closer to Epcot (International Gateway entrance) and Disney/MGM Studios.
Vero Beach and Hilton Head are, obviously, located on the coast, away from WDW.
They all have similar (not exact) room layouts available. The room amenities are all similar and very nice. The theming is different from resort to resort, and is up to your personal preference.
Just pick the one that looks best to you and has availability for a stay, and then try to visit the others while you're there.
Of course, Saratoga Springs is the one currently available for sale, unless you're considering buying a resale, then they all are.
Good Luck! I hope you enjoy DVC as much as I have.
