Our dulcimer group is often asked to play for upper elementary school classes. We've had great fun with "Soldier, soldier won't you marry me." We take along props including a tricorn hat, breeches, Jefferson shirt, buckle shoes---and a woven market basket. We find a girl and boy willing to act out what's happening as the song progresses.
For many upbeat American folk songs suitable for children, find copies of Ruth Crawford Seeger's books: "American Folk Songs for Children," "Animal Folk Songs for Children," and "American Christmas Songs for Children."