I was able to get fastpass reservations for Avatar: Flight of Passage for my husband and myself, but my daughter (2) and son (turning 5 during the trip) are both too short to ride.
That leaves my son with a tier one fastpass available, but he can’t ride anything by himself. I don’t really want to waste the fastpass, so I considered just putting on his magic band and riding a Avatar twice. 
I also considered putting on his band and taking my daughter on the Na’vi River ride. That doesn’t seem fair when he’s already waited for me and my husband to ride Flight of Passage (which is really rich when you consider the many many times he’s going to get to rider switch rides she’s too short to ride.)
I read this touring plan blog that says when in doubt, beg. I suppose I don’t have anything to lose, so I will try to ask if my son can ride fastpass with my daughter and I even though he doesn’t have a fastpass.
Here is my question (finally!): Would it be better to make the Na’vi fastpass with my magic band and the Avatar with his, so that when I go to the cast member I am legitimately the fastpass owner and asking if I can take my son so he isn’t left out? Or would it be better to ride Avatar with my band and ask the cast member if I can please ride along accompany my kids since they are too small to go alone? It’s a small distinction, but it seems like maybe it’s important to present it the right way.