You do need to choose a park and a day you want to visit before you can print your voucher, but that information does not show up on the voucher, and I was told that you can actually go to either park, any day the voucher is good, no matter what you put when you printed it.
I am not sure I am following this right, but I printed my vouchers the day they were emailed to me. I didn't have to put in a date that I wanted to use them. The vouchers do not specify any date of usage, just black out dates.
Here is what it said in the email:
"Just print out your vouchers to redeem it for your FREE tickets to a Walt Disney World® Resort Theme Park, or, if you prefer, you can choose to donate your tickets to a designated organization. It’s up to you!
If you choose to redeem the voucher for FREE tickets, be sure you bring the vouchers and valid photo ID to Walt Disney World® Resort to receive your tickets. Then go off and enjoy the magic! "
And here is what is printed on the voucher:
"Thank you for volunteering! To redeem this voucher :
Present voucher and valid ID at a designated theme park will call ticket window. Valid
ID is one of the following : driver's license with photo, or a government-issued passport
or photo ID. If under age 18, you can instead bring an original or a copy of a birth
certificate (school or children security IDs not accepted).
•
Voucher is non-transferable, revocable, not for sale or resale, and is void if altered.
The Guest whose name is preprinted on this voucher must be present at time of
redemption.
•
One-day, 1-theme park ticket must be used on the same day as redemption. Ticket
is not valid for admission on March 29 - April 8 and July 4, 2010.
•
One-day, 1-theme park ticket is not valid for admission to a Disney
Water Park, DisneyQuest® Indoor Interactive Theme Park or
Disney's Wide World of Sports® Complex.
Instructions for Annual Passholders and multi-day ticket
holders redeeming voucher for an alternate option instead of
the 1-day, 1-theme park ticket.
Present your valid ID, this voucher, and your valid multi-day ticket or
Annual Pass at a theme park will call ticket window to redeem for a
Disney's FASTPASS® Special Exchange card or for a Special Ear
Hat figurine with unique trading pins.
Instructions for Guests redeeming voucher at the
Disneyland®
Resort in California
If your plans have changed and you would like to redeem this
voucher at Disneyland® Resort in California, simply present your
valid ID and this voucher at a Main Entrance ticket booth. Your
voucher may not be redeemed for admission at Disneyland® Resort
on the following dates : February 13 - 14, March 21, June 21 - 22,
July 4, November 21, and December 11 - 12, 2010."
I read this thread and after a few pages of wondering why y'all weren't getting slammed about making comments about not getting in on the promotion, I saw that it was begun on another board. You even mentioned not to voice these opinions on the Budget board because you would get flamed. Then the mod moved it to the BB and the very next post is slamming everyone for being disappointed!

You were right!
I personally would agree that how this promotion has turned out has to be disappointing to some folks. And I would be willing to bet money that those who are flaming them for voicing their disappointments have gotten their tickets. I would be disappointed if I hadn't jumped in on this early enough to get my tickets. I already volunteer at the school every week, so I don't feel one bit guilty about taking advantage of free tickets by volunteering at one of the listed organizations. And actually, they weren't free to me, the 20 gift baskets we made for Meals on Wheels recipients cost us about $75, so we definitely cannot do this again. If someone wants to find a way to flame me for this, have at it.