One of our most magical moments at WDW occurred in just this situation. We were traveling with another couple and their dd..same age as my dd. The girls were about 7ish at the time.
The girls had been dropped at the NeverLand Club for the night, while the adults headed to California Grill. When we got back to the Polynesian to get the girls, we went out to the valet desk to get a cab back to POR. The guys there said, nah, you don't want a cab. Come on, we'll take you. So into a WDW white van we hopped, and they took us back. It was really fun to get to chat with them. Now, I"m sure that based on the time of night and it's not being very busy, these kids figured it was a nice break and they would probably make a decent tip...which they did. So, it's nothing I would count on happening again, but it was nice.
The funny, and somewhat sad, thing about that??? The other guy we were with is known for his 'money saving' attitude. So, he whispers to my dh...'So, do we tip these guys?' to which my dh replied..'Of course.'. The other guy says...'How much? Like two bucks?' I thought my dh was going to slug him!!! He told him to tip whatever he felt he should. So, the one guy tips $2, while my dh tipped them $10.