St. Maarten on your own is very easy and with young kids a must. But that is just my opinion.
We (myself, DH, DD's 12, 10, 8, 5) spent a week in St. Maarten last December. We had a great time all around, but had to improvise a few times to keep everyone happy. Luckily we at the Maho for a wedding and 30 other people came too.
We took the kids into Philipsburg on the Monday - busy day (4 cruise ships in) and they liked seeing the ships, the shops and people and the school in the middle of Front Street (they loved the uniforms and how cute all the students looked) but after about 1 hour they had enough of the crowds of people and just wanted to go back to the resort and swim.
So the next day Dh and I went into Philipsburg on our own - good thing. The Disney ship was tendered and that is what got me hooked on a cruise. But so were 5 other ships - it was a zoo on Front street and I saw many unhappy kids going from shop to shop through too many people.
The next day we rented a jeep and toured the island on our own - now that day was fantastic. We stopped in Marigot, stopped at the "border" sign, stopped at the far end of the island and kids ran and played in the shallow waters. They loved driving through the island with the wind in their hair and being able to stop and explore whenever we wanted. (Makes kids much more happy to have a little input of when to stop).
We loved St. maarten and will go back again! But first it is
Disney Cruise time.