Have you reviewed this site, for learning piano:
https://app.hoffmanacademy.com/lessons/
I am currently teaching my 6 year old and my 3 year old how to play piano and guitar. We have gone through enough of his videos that I can honestly give his site two strong thumbs up.
As far as I can tell, all his videos are free. If the parent knows enough about music, they can use the free videos to supplement any beginner music curriculum.
I enjoyed his videos enough that I purchased his premium lifetime membership, which comes with workbooks and games. But my kids are young and I haven't made them work through workbooks yet. I'm trying to make it as fun as possible so far.
I have no affiliation with Hoffman Academy. I just think he's a great teacher.