We had 4 people, 4 bags, gave $20. We walk off with our luggage so no need for a disembark tip.
The one time we did have them take our luggage many years ago, I don't remember there being anyone we could have tipped though. They collect the luggage from the hallway in the evening, so we didn't see them then to tip, and then we collected it ourselves by searching in the luggage area and then put it in our vehicle; there was no one there that helped us in any way. But this was many years ago and maybe it's different now. Or maybe it's different if you're debarking and getting on Disney transportation.