Buy pizza dough and let older kids make individual heart-shaped pizzas. Have heart-shaped sugar cookies ready before the party. Kids love to make fancy, ornate valentines. Search your craft store for unusual or special trim supplies. At the party, provide red, pink, and white paper, along with items like heart stickers, heart doilies, glitter, ribbon, stick-on jewels, glue, etc.
Young children can make valentine placemats to use at the party and then take home.
Decorate red, pink, or white construction paper with drawings, heart stickers, doilies and other two-dimensional trim. Then cover both sides with clear adhesive vinyl paper. Make mailboxes at the beginning of the party, so guests can mail notes and valentines to each other. Cut one paper plate in half. Turn one half over and tape it to the first plate, so you create a pocket.