I took a
Galapogos Islands Cruise last year with my kids, which they loved. Lots of wildlife to see in the Galapagos Islands - they really enjoyed the cruise.
In reality, the kids should take care of themselves - cruises often has lots of facilites and kids clubs to keep children occupied, so parents can equally enjoy the vacation.
Just make sure you take some pills incase the children get sea sick - that would be my tip!