Take one empty soda bottle, decorate with fins (not Finn’s) and favourite footie team adornments, and weight with a tennis ball…
Place on compressed water+air thingy, engage safety goggles, and retire to a safe distance before signaling eldest son to launch!
Watch soda-rocket woosh several hundred feet into the evening sunlight to the ooohs and ahhhhs of the other cub parents. If I’d known cubs was going to be this much fun I’d have joined up too.