For St. Maarten, I'd reccommend Orient Beach. If you go with an excursion, they'll have chairs, facilities and food for you. We tried to find a better beach last visit and could not. For St. Thomas, I'd do the Trunk Bay Beach excursion to St. John. It's extreemly relaxing and has the most gorgeous scenery. I have never been to Magens Bay, I heard it was too crowded, and we don't like that. You can check the number of cruise ships that will be docked that day on www.VInow.com
. If there are more than 3 ships, I'd avoid Magens. Others have said Magens is nice though and since I've never been there, I couldn't say.