With every possible motorsport option open to them a lot of F1 drivers choose to do Kart racing as R&R when not working - They obviously dont find it booring.
I have driven in a few Kart endurance races and would place it as at least as much fun as the open wheel single seaters I have driven - Different but in its own way just as thrilling
Never driven a gear change Kart though, the races are so wheel to wheel and hectic its hard to know when you would have time to change gears!!
Have a go and I bet you come out grinning.