I always tip $3 for drop off and $3-$5 when I pick it up. I know that might sound excessive, but we are on vacation and I find the valets very pleasant and very honest. They once found my credit card case and left it on the seat for me. (It must have fallen between the seat and the center console.) Everything was in tact, even gift cards, so that's why I always feel very generous towards the valets.
Also, we only use the car two or three days of any trip, just for AK, MK and MK resort restaurants. We plan on doing all of our MK stuff while we are staying at the BLT this trip, so we'll only be using it to go to AK while staying at the BWV.