They were pretty simple. We found a big bag of slinky's that were reasonably priced in a party supply store. I used blank business card stock for the card and made a message with address labels.
If you have Avery 5160 address labels here is a printable. Use a paper hole puncher in the upper left corner. Add your message to the back and slide on the slinky.
A super easy project that a second grader can assemble himself and no sugar involved. Woot!
Happy Valentine's Day!