I just got in from my first ever parent-and-child karate class. It was great fun, and reminded me of how excited I used to get when my dad would play in the parent-and-child hockey games when I was young. The class was just run like a normal kids class--no tailoring it to be more suitable for parents. I think more clubs should try this type of event. It shows the parents how hard their kids work and why they like to go to the classes in the first place. It's both humbling and a good bonding excercise.
(Now, after class, my son is wiped out and fast asleep in bed. And I'm sure I won't be awake much longer.)