Not all housekeeping cast members even know how to do towel animals. I don't know how you would request a housekeeper to do that, as the front desk may not have any idea who is even assigned to clean the rooms.You may have a room request that is more important than a "maid" request, too. And depending on the day, you may have different house keepers. Although I tipped both maids durung my AKL stay (11 nights, $100 total),neither of them left anything except a very clean room and bath area. I believe it is the luck of the draw, not tipping. I have stayed on property 15 times, and never once gotten a towel animal, but if I bought stuffed toys and/or beanies, and left them out, they were often arranged in the window (mod and value) or on the bed. At AKL and CR, I just got a spotless room.
Best of luck in your quest, I hope your boys won't be dissapointed next time. Maybe you can leave out some toys and get some fun that way.