I never schedule anything. Instead I make a list of all the things I would like to do and then each morning wake up and choose from the list. Here are a few from my trip last year with a 5 and 8 year old.

Salt Pond Snorkeling and Drunk Bay exploring ( this would be great for the 8 year olds)
Cinnamon Bay (great kid beach, make sandcastles)
Maho Day (Sunday there are a lot of locals there with their kids)
Lunch and Beach at Vies (the chickens and cats running around will be fun for them)
Park at Caneel and hike to Honeymoon
Villa Gravity day- let everyone relax at the villa, kids in the pool, parents chilling out with a rum drink

There was someone on another forum that planned every day to the minute and came back to say that he ended up having to cancel some activities at the last minute because it was just too much. Don't overplan, just plan to enjoy every day, no matter how much or how little you do.

For us, just 4 adults, it's fairly simple:

Wake up...drink coffee

Make dirty jokes.
Sit by the pool
Yell at me to fire up the grill for lunch.

At about 2:00, I open the map and pick a beach to go to for the afternoon's snorkel adventure.

I suspect when our daughter starts joining us, this will still be the routine.

We schedule only 1 day; our off-island/boat day. I schedule it around the cruise ship schedule so we're off island on the "busiest" day

Three eight year olds, trips I would guess...wow.

With three kids not fully out of "whining age"...mine are 6 and 9...(so I'll use mine as a reference point)...things will be alot different than just adults going...with kids maybe---

Trunk Beach one day then lunch out

Maho beach one day

I've heard the horseback riding is fun

Do an "easy" afternoon hike to ruins(and maybe "picnic lunch") one day...maybe annaberg or the ruins above waterlemon off of Johnny Horn trail...

Lunch in Cruz Bay then some shopping at Mongoose Junction...

A day trip out to the east end with a stop at Vie's for lunch and then find sloop jones' shop and get some tie dye t-shirts...

I plan on getting the kids to the beach each morning and try to pack a lunch. My kids are nuts for snorkeling. Another activity they love is horseback riding with Dana at Carolina Corral - 1-340-693-5778. She usually calls back the next day. I drop my kids off and do a short snorkel trip.

Check out seestjohn.com for the life music schedule. Its fun to grab a drink somewhere the tunes are rolling. Sunday Jazz at the Beach Bar is great, and the kids love playing on the beach.

Cheers, RickG

thanks to all...excellent suggestions....certainly not going to go "grizwold" and overschedule!