Draw a hopscotch grid together, then let your child invent one extra rule: hop backwards on the fours, clap on the sevens, turn around at the top.
Play it exactly as they specified, including any rule that makes it harder for you.
After a few rounds, ask whether the rule works or needs changing. Redrawing a rule that turned out badly is part of the game.
Hopscotch already combines balance, single-leg control and sequence memory. Letting the child author a rule adds design and negotiation, and having to obey their own rule is where they discover that rules have consequences for the person who wrote them.