besides different kinds of dolys and glue stix, cut out heartsin different sizes, thenshow the kids how to makeanimalss out of them. EG, fivehearts, rounds sidedown stacked next to each other make a caterpillar. one big heat placed sideways, with the point of a smaller heart in the indent of the larger one starts a fish. Kindergartners love to copy simple samples that you make. This will make a great valentine once it is glued down.
Don't have kids sign dzens of valentines for the class. We had kids make one valentine from the class. The children make and sign it and put it into a bag. Eeveryone who makes one for the bag gets to pull one out. That way you don't have the the disicipline problem of keeping kids occupied while you wait for everyone to pass out the valentines and you don't have hard feelings when certain kids don't get valentines.
Another idea if you have access to a microwave is to make chocolate dipped pretzels for them to take home for mom and dad as a valentine's day present. They need to be supervised by the melted chocolate, but this can be made at the beginning of the party and be bagged to take home in a few hours.
Hope this helps.