Since you're from Michigan and the kids will be taking their 2-week vacation with you, I'd highly suggest Gulf State Park, Gulf Shores, Alabama. Snowbirders can stay there the whole winter/early spring season - no 14-day rule. They have monthly rates. The sites are big with full hookups, a clubhouse with activities and potlucks, and the whole park is filled with snowbirders, including many from Michigan.
The beach is beautiful but in December the kids won't be swimming - but kids are tough. It's a great area for biking - nice and flat. You are within a short bike distance to town where there are many nice restaurants and shops. You can also purchase fresh shrimp from the boats. During the holiday season you can take your car on the short ferry ride over to just north of Dauphin Island and tour the beautiful Christmas displays at Bellingrath Gardens. The whole area is a great place to be during the holidays. You can also do a easy daytrip to Pensacola, FL and perhaps there will be an air show going on.
This is a very popular park so make reservations now.
Full-Timed for 16 Years
.... Back in S&B Again
Traveled 8 yr in a 40' 2004 Newmar Dutch Star Motorhome
& 8 yr in a 33' Travel Supreme 5th Wheel