Consider a beach sailing holiday?
I've found Sunsail to be very good at these, running day long creches and junior activities so you can get out on the water for as long as you like. In fact their holidays tend to be dominated by couples with young children. Of course its sailing in dinghies or smallish day sailers, returning to the same base/hotel each evening, rather than proper cruising. But its still great fun, with lots of activities laid on. I would say you will enjoy this more than a cruise with a 4 year old who is not acclimatised to sailing.
Otherwise I too would encourage you to consider flotilla sailing. It is definitely not a singles/party thing, except for certain specialized holidays. You get your own boat (assuming you are a competent sailor) and most boats will also be rented by family groups or close friends, couples. The average age is a little older than the beach holiday, but there are still likely to be other children in the flotilla with whom your child can make friends.
Last edited by LynW; 12-04-2007 at 02:43 AM.