How would we know the name of the person if we don't see them? Well, I will play it by ear when I get there in October. If I have some smaller bills, I will leave something each day. Again, I am only there from mid-day Friday to Sunday morning, and only two nights are involved, so it won't be a fortune I give them. If I don't have anything smaller, I will just leave the whole tip at the front desk when we check out.
I believe (at GCH at least) there is a small tent card in the room (maybe on the sink?) with the name of the regular mousekeeper.
Another reason to tip every day (rather than just once at the end) is that you might get a few extra-special touches if the mousekeeper knows you appreciate his/her work.