Here's how we did it!
Using the free Mal's Spell Book template from www.GrowingUpBilingual.com, we used the book cover of the template and printed it out in postcard format on cardstock. We printed out the party information on a separate piece of paper and glued it to the back of the printed template, added a little glitter and voila!
Template: http://growingupbilingual.com/2015/crafts-2/descendants-party-invitation-tutorial/
We were forced to stay inside for the party due to weather, so we had to be creative with game locations!