Fastest way to link a one day ticket

[jjskribs]

My husband and I are AP holders and we are taking a short trip to WDW at the beginning of May. We just found out that our son is going to be in the Orlando area at that time and would like to join us for a day in the parks. What would be the fastest way to obtain the one day ticket so that I can make a few fast passes for that day. The Disney site says it takes 14 days to receive the ticket. If I purchase through them do I have to wait for the ticket to arrive before I can link it to MDE or can they do that when I purchase it? Would it be faster to use Undercovertickets?

 

[KathyM2]

I thought that if you purchased directly through Disney, they would give you the reservation number immediately so you can start making FP+ reservations...