A relay race, where each handover the next runner has to carry a silly item, extra large things that will make it tricky for them.
like inflatable dingy/bed, large beach ball, wellies, washing bowl with washing in, oversized cloaths, water bombs, ballons full of flour, empty 2L water bottles, etc.
Anything that makes them have to think a bit about how to carry all the clobber.
Add a few bales of hay to clamber over or car tires to step through, to make the going slightly tricky.
Have the runners who have doen their run, use water pistols in a section, to spray runners as they pass, well you get the idea 😉
Winner is the team across the finishing line with all the clobber 😉