I'll add a kids menu to this thread (or the start of one):

-- before you let them swim off the boat at a new location, go in yourself and assess the current/wind/drift
-- take them to Scrub Island for a night half way through and let them play in the pools and shower
-- fit them with snorkel masks at home before leaving
-- if conditions are relatively mild, take them to the Bubbly Pool for sure
-- take them to the Baths late in the day when it's not crowded and let them play hide and seek, etc. on the trail to Devil's
-- take them to Happy Hour at Saba Rock
-- bring some boxes of their favorite mac and cheese from home; the food part is generally very easy--you can provision for some stand-bys they eat at home, and most of the restaurants onshore are of the fries and burgers genre
-- don't let them apply their own sunscreen even when they get to the age of insisting they can do it themselves
-- bring long sleeve surf/water shirts for them and try to get them to swim with them on as much as possible
-- a teenager or prototeenager can be nicely encased in the v-berth and an entire day can get underway happily for the rest of the boat without needing to bother with getting them up and prying them out of there
-- bribe them with stops for t-shirts/dresses and virgin coladas if you happen to hit any low morale spots
-- (I know this will be a minority view!) don't allow soda as a regular beverage at home but have a rule that everyone gets cold Cokes whenever they want on the boat
-- have them bring the phone but cutoff data access; no texting while there but take lots of pictures with their phones and do the instagram thing, etc. with their friends on the way home
-- if you have girls, find a compromise system with the water that will allow you to let them wash their hair once a day in fresh water, however briefly; and a small amount of Joico K-Pak styling oil combed in after works great for dealing with the sun and salt to prevent development of a bird's nest and hair bad mood
-- everyone says see Pirate Show at Leverick too, though that is typically done for the season when we charter
-- Willy T is (usually) ok for them early evening on the lower deck on the kitchen side; the food is good and the funny restaurant boat you dinghy to is a fun thing for them
-- bottom line is this is better for them than anyone else regardless; BVI is a total water world and I don't know any kids who don't want that in their dreams