Kite flying while sailing is a good bet, too - for little ones.
And I wouldn't discount the kids helping out with tasks on board. My 4 going on 5 loves to have certain jobs that are her responsibility - she practices getting
fenders ready - she grinds
winches -
We also have some fun games - magnetic words - we have little picture dice that she makes stories out of- washable
paints are great too!