Mike, I would recommend Eastern Caribbean for your first.
Regardless of the line you choose, there are many options for entertainment on the new mega-ships such as the Crown Princess. On smaller ships not so much. but there is still plenty to do.
Most people on cruises are very active during the day so most people do not want to stay in the bars all night, but some stay open fairly late.
The pools do close. (On every ship we've ever been on at least.)
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RichStacy
Landlocked in Denver, but cruisin every chance we get.
Polynesia, Carib. '86
Cr. Odyssey, Scandinavia, '91, 30 Day S Pac. 2002
Crystal Harm, Aust., N.Z., '94
Royal Odyssey, AK,'96
Old Cr. Pr. Canal, '97
RCCL, Carib, 1998
Volendam, Car, 2000
Ryndam, 35 day S. Am., Antarctica, '03
Is. Pr., Canal, 2004
Statendam, 34 day China, Japan, AK '06
Cr.Pr., Carib. 08
Eurodam, Atlantic, Med. '10 Golden Princess