Make sure you take the sanitiser and boil the bottled water in your in room kettle (i`d clean, boil & sanitise the kettle first)most hotels give you bottled water every day to brush your teeth with.
But the biggest worry would be getting shower or bath water in your childs mouth, I would suggest sponge bathing your child.
hope this helps and have fun.
Thanks for your help. Have a great Bali holiday!