I just drove to the post office and mailed all of the cards. The worker there said that they should all get there in time, possibly even the ones going overseas since they take 5-10 days.
I found it interesting that I needed special stamps for the ones going to Spain, but all of the others cost the same and were just a regular air mail stamp. It costs the same to mail a card to Canada as to Finland and New Zealand and the UK, but not Spain?