Ha, I know what you mean about sleep, s&k'smom! Good news for you though, you can check in with the voucher. Sometimes they will make you come back to the front desk later in your stay to show that you did in fact exchange the voucher for the actual AP, but they most likely will not, and accept your voucher as proof. In fact, whenever we have checked-in with an AP rate, we have never even needed to show the AP. Even when a trainee checked us in, neither he nor his supervisor asked about it. And you'd think a new person would be on top of rules like that when he's being watched by a superior.
If you do stay at WL and choose to activate it before you check-in, I would just take the boat over to MK and activate it there. It'll be the closest place to your resort (a little closer than ttc). Oh yeah, you can't exchange them at the airport, only on property officially. That is what the CM told us when we bought our APs at the airport store, but he said that they've done it in the past, but you're really supposed to go to WDW and have that done. I had never heard much about this so I'm not sure if it's true, but that's what he told us.