Just returned 2/22/07. I feel the same as MarthaL. Red beach is fabulous but watch out for those little prickly things, they are painful (aqua socks would solve that problem). We arrived at around 10:30 in the morning and had our pick of cabanas. Bring a cooler and pack a lunch, you will not want to leave this beach. Bring some thick towels so your son could nap on the picnic table along with your book!
Loved Sun Bay beach and there were lots of children to play with (all locals).
Green beach is way to far of a ride only to find a small beach area and way too many power boats that practically anchor on the beach! Good snorkeling but the snorkeling was so much better at Red beach. Look for the tiny pinkish red shells there.
Tradewinds for a great burger and the best french fries on the island. Chez Shack on Monday nite grill nite with a local Puerto Rican band which is fun for all of you.
If you have a place with a kitchen, don't expect to find the foods you are used to, bring those your son can't live with out.