It’s only when you want to let them jump in and out of multiple apps (e.g. pick what game they want to play on their own) that you start having a problem.
(And the not-idiomatic-but-people-do-it-anyway solution for that, from what I’ve seen, is buying one extra iPad, and creating a special whole-family Apple account for it, to effectively serve as a game console for the kids.)
The solution to that is Assistive Access.
It’s more painful to use than it should be, but it absolutely solves this problem.