...and a little (handi)crafty.
For the stuffed heart hanger
Cut two pieces of wool felt and decorate one with pink buttons and embroidery thread. Use a running stitch to attach them together, being sure to sandwich a looped ribbon at the top. Stuff with a bit of batting and sew closed. Hang on your favorite little sister's bedpost.
For the printed paper valentines
Inspiration here! Cut hearts out of styrofoam. (We have these sheets since we do lots of printing projects, but you could also use disposable plates.) Use a dull pencil or wooden stylus to decorate them with designs. Roll printing ink onto the hearts, then stamp onto red squares of construction paper. Address to your best friends and pop in the mail!