Generally speaking, if it does not look like it is fun, kids are not going to be attracted to it. If it is not fun, kids will not want to stick with it.
There are exceptions but they are few.
Which is why most successful kids programs in aikido work very hard to make it fun but also do it in context of teaching things like Rei and tradition. Otherwise it is just glorified day care. Besides, it's not like having fun and teaching etiquette and tradition are mutually exclusive.
And in the decade or so I've had teaching kids what I've noticed is that the ones who continue are rarely the ones who came only for games and fun. They find the Aikido fun. They become interested in the tradition. Then they start to understand the Rei and how it figures in. Heck, I've got kids who are better in terms of proper practice than some adults. Because they take it *very* seriously. Which is as it should be.