Please tell me you have a younger child, you may not like hearing this, but three year olds should not need a warm bottle , or any bottle at all. No wonder they are not toilet trained. They are not babies anymore.
And why do you need to stay with them in the playroom?Are you nervous or are they? You might make them nervous if they aren't ever left on their own with kids their age. The counserllors are very well trained( most have teaching certs for preschool) and most kids love the playtime.
I have three kids and by three they should not be on a bottle, period, ask you dentist about that if you think I am just being a meany. They should also be toilet trained with just " accidents" happening occaisonally and perhaps at night.
I assume they are unable to attend preschool as most require toilet training.
They will not be allowed in the kids programs unless trained, but frankly, just don't mention it, and only leave them an hour or two, and you should be able to get away with it.
Yes they have milk on board, I think it was 2% but that will be fine for a 3 yr old for a week( ask your doc) , milk is available at meal times and on the buffet in the morning they have the little cartons of it for cereal, pick up a few and put them in the fridge in your cabin( all cabins have fridges) for when ever you want them.
Bring a water bottle for them and fill with juice from breakfast buffet also, ( no cartons just glasses) as you will have to pay for juice otherwise( at bars etc.)
Have fun and wean those children( notice , children , not babies)