Upload & Sell: Off
I would like to give you a different approach as I find that giving most people SD cards would be a waste as they would not know what to do with them.
Instead have you considered posting your pictures online to a site that gives people access to view and download the pictures. Both Zenfolio (my preference) and Smugmug are great for this, and it would be a lot easier to upload the pictures here once than it would be to copy the photos to 85 SD cards, and then deal with your relatives teaching them what to do with the cards. If you upload them to a site, you can even setup a custom URL (e.g., www.zenfolio.com/TheJohnsonsWedding) and can include this in the thank cards.
You also don't need to deal with file sizes, card sizes, bad cards, or printing as people can order prints directly from the sites.
I do a lot of local events for the school and sports teams and this is how I distribute the photos. PM me if you want a link to my Zenfolio site to see an example.
Another option that makes it very easy for people to share is to setup a Facebook group page. This is free and you can upload the photos there. Facebook makes it very easy people to share the photos and you can tag them with all of the participants, which people generally love.
Just a thought.