My family and I returned 2 weeks ago. We had a great time among some of the friendliest people anywhere. Realize that this is still an emerging country, not a St. Thomas or St Maarten - 4 power outages during the week, no shopping to speak of, etc., but a bunch of friendly people trying very hard, almost always succeeding, and a place to kick back and relax.
The resort itself was great - they upgraded us to a 2-room suite overlooking the South Pool, with an ocean view, which really helped with 4 of us. I had no problems with service levels, but I/we are relatively undemanding - our Plat amenity that we ordered when we checked in (3pm) and would be delvered in "15 minutes" showed up just as we had hopped into bed at 9pm. No big deal. Other room service orders were as at any normal Marriott - 25-35 minutes.
Feel free to PM me with any follow-up questions.
1) Are there activities for kids on the resort?
My 5 yr old had plenty of fun just playing in the various pools. There is a kids program that takes them for an entire day - a different theme/program every day - but we spent much of our time exploring the island so we didn't use it. There is an arcade for older kids, and a location to check out board games, ping pong, shuffleboard, cards, etc., etc.
2) How are the restraunts? Since they are probably expensive, are they worth the money?
There is a casual place on the resort (Carribean comfort food as they call it) - chicken sandwiches, burgers, pasta salads, good kids menu, etc. that we hit for lunch a few times - $8-12/person, kids are free. The Italian place was pretty decent and the Pizza Shack was about as expected (hard to be real good or real bad with pizza). With a 5yr and 7month-old, we didn't venture to the fancy places. We mostly looked off the resort for food.
3) What are the two top must see things on the island?
Hard to pick two - The Fort, the Batik, the train ride, Turtle Beach (700lb pig and monkeys roaming around the beach), a full-day catamaran trip to Nevis (say hi to Elvis if you go), a rain forest hike, and a full day in the car lapping the island taking pictures were our major outings. I'd say the Nevis trip and Turtle Beach are the "must-do's"
4) Do you need a car rental for the island?
Don't think you "need" one (lots of cabs around), but we always get one. It gives a lot more freedom - we were able to run down to the IGA to stock up on water for the baby, grab some snacks, go out for a late night drive up the mountain to see the stars, go to and return from the beaches when we wanted to, etc.