I have been to Bintan for 5D4N with my 3 1/2 yrs old daughter, they offer a baby club for child from 1 to 12. Their staff will take care of your child from 9am to 5:30pm. You may take your child for shower after 5:30 and take your child back to the baby club after 7:30 and pick them up at 9:30. For the rest of them you can use all the facilities within the resort without worrying about your child.
Do not scare by the high price of the Package, the package are all inclusive of hotel, travelling from airport - ferry terminal - hotel, 3 buffet daily including wine (red, white, rose, beer, xo), insurance, airport tax, freight surplus charges, etc. They total amount you will spend is the quoted price of the Package (excluding massage and spa).
You will spend the same amount if compare with a tour at HK$2-3000 lower than the Club Med price.