We tip only at the end, based on experiences during the week.
Proabably $100 for the butler, and 50 to 70 for the assistant butler.
We’ve tipped $30 or so for exceptional service from others, be they butlers (not ours), waiters we had regularly, servers form the pool/YC lounge, and $20-30 to several bar tenders and the often terrific pool guys. Also tipped the Maitre D’ from $50 to 75 but this was an exceptional guy. On other trips we have not tipped the MD.
Haing said that, we are fairly big tippers, so evaluate the above in that perspective.
We have never felt that a tip was expected and certainly not that the possibility of a tip changed the service level. Staff know that Europeans are generally not tippers and treat every one the same. So just leaving the auto tips in place and nothing more is certainly fine as well. And of course treating the staff with kindness and patience when they are busy.