I would vote for Regent Seven Seas. The pricing is competitive if you are looking for a Caribbean cruise and you will find plenty of 40-somethings. If you are looking for a one week med or Tahiti cruise you will find even more in your/our age group.
"The test of a first rate intelligence is the ability to hold two opposed ideas in the mind at the same time and still retain the ability to function."
F Scott Fitzgerald
Seven Seas Voyager (30nts) - Dubai - Cape Town - Nov 14