I think you're confused about what an AP looks like. It looks like a regular tyvec ticket with the exception that it says annual pass and the passholder's name on the back. It is entirely up to the individual how it's to be carried around. I never let my kids carry their APs as I'm too afraid that they'll lose them. I'm the family ticket holder.
I think that you're picturing lanyards that lots of people wear. These are used mainly to carry things like tickets, fast passes, GACs, money, room keys and pins for pin trading. A lanyard is in no way a requirement.
Hand him his ticket just before he goes through the turnstile and collect the ticket back from him once he's through. Until this past year, our DD didn't even carry her GAC; DH and I did. This year she wants to be the one to carry it so we let her since she's now carrying a purse and seems to be really good about keeping track of the purse (she's rather obessive compulsive about it, something that I encourage; gotta make those issues work for her sometimes).