There is a new Marriott Resort in Palm Beach, FL on Singer Island. This is an all suite resort located on a beautiful beach. Our family owns two MVC timeshares in the area and find it to be a great vacation location. The weather should be nice in spring. If you enjoy deep sea fishing, the Gulfstream is located just offshore, so fishing is very good.
Since this hotel is new, there may still be availability for using Marriott points at this category 6 hotel. The Palm Beach and Ft. Lauderdale airports are within a 1 hour drive, but w prefer PBI for being less crowded and closer to Singer Island. Have a great trip.
We are partial to the Marco Island Marriott Resort. Will be there again for 2010 Spring Break. This place is great for Spring Break and being on the Gulf of Mexico is magnificent. They rent Waverunners right on the beach and have a great tour through the mangroves off the southern tip of the island. Lots to do without leaving the property.
With kids that age -- I'd hit the JW Marriott, Grande Lakes in Orlando. I have been there twice with 2 of our kids (age 16 & 13) in the last year and I think it's one of their best properties in the US. Weather in March/April is good and there's LOTS to do. Resort activities on property to keep teens/tweens busy: beach volleyball, 4 outdoors pools connected by an amazing lazy river, outdoor adventure (ropes) challenge course (photo attached) , golf, life size chess, bocce ball, bike rentals. And if you want to do something off property -- you're surrounded by theme parks galore and great shopping! Bon Voyage :-)