What is the minimum amount of BM/formula an 11 mo should have?

Beebee09

DS is staying at my mother's for a few days next weekend while we go to an out of town wedding.  Since we BF I don't know how much volume he gets on a normal day.  He isn't that great with a bottle and I'm nervous he won't get what he needs.

I'm just looking for a range to tell her that he should probably take in.  Also, if he doesn't take a lot from the bottle will he still stay hydrated if he takes the milk mixed with baby cereal.  He likes it that way and I thought it may be a good way to make sure he gets what he needs.  Not sure if it will be as hydrating, though?!?!