DriveThruRPG[1] has a lot of kid-oriented games. I have Amazing Tales[2] and the kids liked it well enough (although I got a little too scary with the goblins one time and they were a little hesitant to play for a while). At 5 you'd probably be running the same gambit I'd say but ymmv.

[1]: https://www.drivethrurpg.com

[2]: https://www.drivethrurpg.com/product/222950/Amazing-Tales-co...