If the "limited kids" thing is a real issue for you, then make sure you book your Caribbean cruise during a week that schools are all in session (and just because schools are in session in your town, doesn't mean they are in session everywhere -- winter and spring breaks vary dramatically around the country).

Having said that, October should be one of the "safest" months to travel, with that your goal.

Traditionally, I've always heard that Holland America skews the oldest, but I haven't done any recent research on it.

Have you considered Oceania or Azamara or any of the other Premium lines? Costs a bit more, but includes more for your buck, and you don't have the crowding issues at the buffet and the shows.