Generic engagement cards

Hi all,

My future in-laws threw us an engagement party and we received gifts from a handful of guests. I ordered thank-you post cards from Minted.com. The thank you cards have a pre-written message on the other side...reads something like “thank you for celebrating our engagement with us and for your generous gift. Can’t wait to share our special day with you.” Is this tacky? Should I have hand written each thank you note, like I plan to do for the wedding gifts. We spent a good bit on the post cards, but at this point I don’t mind buying more and hand-writing them, if it’s going to upset people. Thanks!