The only "prepaid" tips are to restaurant wait staff. They will compute the cost of hwta you ordered and add both the tax and a 15% tip to that amount. This would also include room service people.
Other tips, such as bellmen, valets, housekeepers do not get automatic tips. Note that even though there is a daily charge for valet parking at the deluxe resort, the valets do not get any of that fee and they are tip positions.
I have been told by several people who work in Concierge tghat they are not allowed to accept tips. If you do get them to take money, they turn it in to a fund.
