Intersting that folks want to remove the automatic tip for their small children when the toddlers often make more work for the steward than perhaps an adult would.
The cheerios on the floor; the extra bed which must be made; the general picking up that always accompanies small children. IF you remove the automatic tip from your bill for any person in your cabin, the steward must turn over anything you privately tip him to the pool.
And...anticipating the next question......Either they are honest or they are not. Their co-workers well know what is a 'norm' or an 'average' that most of them receive in a given period of time unless they are extremely bad at their jobs and they would know if one of them was not a good worker.
Should they attempt to cheat the others, I would think they would not have a very pleasant living experience aboard the ship.