OK, UPDATE on the stop at St. Maarten:
We just got back from the Eastern Itinerary stops of St. Maarten (were there Feb. 17, 2009) & St. Thomas (Feb. 18). In St. Maarten we arranged for a tour with Joyce Prince (I had read reviews about her on cruisecritic.com) and she was FABULOUS!!! She provided a car seat for my toddler, had a cooler full of beverages for all of us in the back of her brand new, very clean, air conditioned American made SUV. She asked what things we wanted to see ahead of time, and was so easy to work with. Our toddler was a little grumpy in the late morning, and Joyce was so helpful, even suggesting a stop for French pastries in Marigot (which did the trick for him).
She will take you wherever you want to go, including spending time at beaches, visiting the "insider's stop" for souvenir shopping, etc. We saw the entire island, got a good dose of history, and stopped for many photo ops. Anything that looked interesting, she would accommodate. We had a tour of 4 hours. My older boys (ages 12 & 14) raved about the tour! St. Thomas could not compare after this, and Miss Joyce.
In St. Thomas, we just took a taxi into town and shopped. It was kind of disappointing. Probably because we didn't see more than the commercialized part, but Joyce Prince and St. Maarten were great! The peace of mind we received from having a safe vehicle with seat belts for everyone and a car seat for the baby were priceless. Just walking up to a driver and asking for a tour is not going to get you those ammenities. The price was $40 per person (baby was free), another 2 people were supposed to be with us, but they bombed out at the last minute (didn't take their cruise, or something), so we had the "private" tour for our family at the "group" price, but I still think it would've been just as great even with 2 extra people.