Thanks for the complement

. . . . I guess my obsession with all-things cruise related comes in handy sometimes

. . . I don't work for Disney (although sometimes I wish . . . .), I work for a major automotive manufacturer (located in Dearborn, MI)

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Beaches near the ports, let's see . . . .
Key West is not much of a beach stop. Most of the shore is rocky, although there is a beach area at Fort Zachary Tayler park if I'm not mistaken.
Grand Cayman has 7-Mile Beach just to the north of town (and the tender docks). Very easy to take a cab from the docks to the beach. Actually, you'll be taken to a beach area by one of the resort hotels. I don't know that much about the prices for chairs, etc as we've done the Stingray City trip on our last visit (and planning to do the same on this one). Check out cruisecritic for additional information about the ports.
Cozumel has some wonderful beach areas on the leeward side (port side) of the island. We are planning to grab a cab down to Paradise Beach ($12 each way). There is no charge to use chairs and umbrellas (they do ask that you buy some food and/or drinks), and $8 to use the water toys.
If we end up going to Costa Maya, I've read that the little village just south of the port (Majahaul?) has some very nice beach area. Cabs are $3 per person.
I can't help you too much with the spa questions as we haven't tried any on
DCL yet. From what I've read, the new spa suites on the Magic are very nice (although a bit pricy if you ask me). Also, you can't go wrong with a cabana massage on CC.
I hope this helps, anyone with addtional info please chime in . . . .
I guess this was an OK 500th post on the DIS. Hopefully we'll get our docs today and I'll join the dancing . . .
Rick