Hi, Sherry!
When you purchase a voucher online for Park tickets or Annual Passes, they will not activate until you use them for entry into a Theme Park. This makes it really nice when you want to purchase them ahead!
It is correct that as an Annual Passholder, you can take advantage of purchasing tickets to
Mickey's Very Merry Christmas Party at a discounted rate! Please keep in mind that there are select days in which those discounts are available. Once you're signed into your online Disney account and click to purchase tickets, you'll see the available dates in blue. I recommend that when you check in to your Resort hotel, use one of the computers in the business center to log in and purchase your Party tickets, that way you'll still be able to get them in advance provided they are not sold out!
Thanks so much for stopping by the Moms Panel, Sherry! I sure hope this helps!
Wishing you a Pixie Dusted vacation!
~Jackie