I've been there quite a number of times so let's see if I'm of any help.
1) There should be no problem with your kids, the petit club is very experienced and very good. However, I think you need to pay extra if they were to join. Only the Mini Club is free, but that is for children from ages 4 to 12.
2) There is free practise golf, with equipment provided. But if you want to play in a course, then yes. You have to pay more.
3) It really depends on the sea. If the current is too strong and dangerous, then they might not have water sports for the day. But normally if it isn't raining during the monsoon it should be fine. That is if the rescue jetski is in working order. The one at Ria Bintan has a knack for breaking down.
4) At circus school, you basically do the trapeze. Believe me, it's enough to preoccupy you. And it's really fun! For kids there is also a tightrope, but the mini/petit club will most likely bring them there.
When you reach there, be sure to check the notices of timings for each activity.
Please login or register to reply