AP vouchers can be turned into AP's at a place with a ticket machine, either the parks or guest services (all the parks and downtown). You can also purchase AP's at the same places. Some resorts have AP vouchers for sale (varies on resort and reported happenings) and you can purchase them there but you still will have to go the park and exchange for the actual AP so that woudl be a waste to stand in line at both places, IMO. TIW card can ONLY be purchased at guest services (all 4 big parks and DTD, I'm not sure about water parks) and prior to your trip thru the AP line. If you purchase at Guest Services in the parks you may receive a temporary card to use (some reports now state you can get the permanent card then). TIW cannot be purchased at any resorts.
So my ? is if you know you are going to purchase AP's for other family members and TIW card, why not just do it before you arrive? Then you will have TIW already and vouchers for AP's and it will be one trip to guest services to just turn coucher into AP's. Unless you are using GAD o MYW tickets to upgrade or a gift card to pay for them I cannot see any reason to wait and purchase some AP's when you arrive.
