kaffinito - I would say just self-park. It's been very convenient for me in the past. This way you have your keys and you know where you're parked. I like the idea of telling them once you're in the lobby

Which building have you requested? I can't remember... anyway, if you end up on the TTC side of the GCH (Tokelau, Raratonga, Niue, Hawaii, Samoa, Rapa Nui, Tahiti), returning to your car for your luggage will be easy. Or will you have a ton of luggage and need help from a bellman?
If you're going to need a bellman, and want to surprise the children once you're in the lobby, I would say self-park... walk in and check in and then retn to your car and proceed to valet and let them take it from there...Hope this helps but I'm afraid it won't