You are considering two wonderful resorts. I love them both. Ultimately I would base your decision on your vacation budget as both resorts are very kid friendly.
At the
Polynesian, you’ll be welcomed with warm hospitality. The advantages here are monorail access to the Magic Kingdom and Epcot, large rooms, access to many restaurants (at the resort and nearby) and a fabulous zero entry pool.
At the
Caribbean Beach, you will have bus transportation to all WDW destinations. The rooms are smaller with two double beds and compact bathrooms. You’ll have a larger food court (kid meals are served in sand buckets) and one on-site restaurant, Shutters. However, in June 2008 the main pool at Old Port Royale will still be closed for renovation. The quiet pools have remained opened. (If this was my first visit, I would not want to stay at a resort with an on-going construction project.) There are playgrounds scattered throughout the resort on the beaches.
Both resorts are tropical with lush vegetation and sandy beaches. The Polynesian and Caribbean Beach Resorts offer marina rentals.