Hey there! I haven't been posting much but I just wanted to comment on your idea to go to Magen's Bay. We were there last year on another cruise and it is absolutely a gorgeous place! We caught a van off the ship and I think it was $8 pp each way. The guy came back to pick us up at the time we asked him to. He also stopped at the overlook on the way back so we could see the island and our ship.
I don't know how much the excursion is but that gives you an idea of what we paid. There is a little bar/restaurant there where we got beer & sodas.
They say you really can't snorkel at Magen's Bay, but we did and the kids saw a few fish. It's just not the best for that. Also there are not wave runners or parasailing there either. But it is so beautiful. The water is all those shades of Caribbean blue, it has gentle waves, and the beach is edged with many palm trees to sit under for the perfect Corona ad pic!
One note of caution though (and I am sure this is true at many beaches, not just this one): be careful laying in the sand! My oldest son came down with a nasty rash the day after we were there, and he was miserable. He was the only one that had laid in the sand, and we think he got sand flea bites. He was miserably itchy for the next 3 days. Fortunately it was the last stop on our trip.
I think this time we are going to hit Sapphire Beach or Trunk Bay.