Kids yo-yo club ideas

Hey everyone. I started a yo-yo club with my son’s third grade class and it had its ups and downs (sorry for the pun) and I intend to do it again with his fourth grade class. Wondering if anyone has ideas to keep kids interested and make it more structured. I want a reward program that isn’t just giving away yo-yos and not having the kids stick around. Just fishing for ideas or anyone who has experience. Thanks for the help. Everyone here has been awesome so far!