after you’ve hooked the fish. The look at bugs with them. Then get ice cream. Don’t fish for too long and make sure they still want to be dishing when you leave.
Later they can see and set the hook (and then fight the fish like they’ve already practiced with you) but you may still need to cast to get the fly out far enough.
Finally, when they can cast sufficiently, they’ll be able to do it all on their own, but you might need to help with releasing.
My 8 y/o can do all those himself now, but needs help casting sometimes depending on how far it needs to go.
At 9 y/o my kids can really do it all on a stillwater.