@Pillagenplunder@lemmy.world has the go-to suggestion: you can't go wrong with giving Avatar: The Last Airbender a shot. I don't know if I'd say it has similar themes or notes to Demon Slayer but it is an absolute winner.

I also highly recommend the movie Spirited Away if you haven't watched it together yet. It's got some similar themes and notes more suitable for the whole family. Instead of stopping demons with violence, Spirited Away finds diplomatic ways to deal with spirits. Also just a masterpiece of a movie.

I'm having trouble thinking of similar anime series for a younger audience but there are some other anime-inspired (like Avatar: TLA) cartoons that deal in similar themes. Steven Universe follows a group of heroes that stop corrupted gem creatures in hopes of curing them. And Star Vs. The Forces of Evil is about a Sailor Moon-like princess from a magic realm that travels to Earth and fights the forces of evil with her best friend trained in karate.