Revert to childhood and cut hearts from folded papers; use these later do make a project in their chosen craft.
Decorate heart-shaped cookies; even grown-ups enjoy this activity.
Make yo-yos of red fabrics they have each brought to the gathering.
Using scraps of threads, fibers, beads, yarns, fabrics, or decorative items, have them each make a small heart-shaped pin to trade within the group.
Have them each the story of how they met their Valentine.
Wish I could be there with you all; it sounds like a lovely afternoon.
Jan in VA