It depends on how long are you going actually.
previously went for 3days 2 nights.
1) Brought my whole family for a flu jab. as i think going to indonesia is a must
2) drinking water try to bring one bottle of 'singapore' water for toddlers as fear the water is dirty. Or you may boil some water in the hotel room.. as for adults, best is drink those minerals water..
3) usually batam can buy alot of children clothes at shopping malls.
4) Please bring mosquito repellants in case.