Unlike Halloween Ephemera, vintage Valentines and post cards are pretty easy to find, and inexpensive too. Check ebay and etsy as well as antique shops, and collage your findings into notes and decorations. Or, if you're out of time, buy them from me! VintageScraps.etsy.com
I'm a mom of 3 teens, wife of one husband, former teacher, retreat speaker, and youth leader, present collage artist having fun with vintage papers, antiques, mixed media, and sophisticated sarcasm!
Check out my shop sometime-
http://VintageScraps.etsy.com/