Thanks for your feedback! About "get the balance right in terms of volume of tasks and granularity" I think that our approach should be to suggest that points are equivalent to money.
The problem by keeping it verbal is tracking what has already been done for an specific goal. Many parents may forget any “verbal agreement” with their kids.
I don’t understand your question clearly, but the idea is to incentivize children to “earn” points after completing tasks, so you are giving value to their “work” with points that they can exchange for rewards. If I would give a “learning objective” could be to teach children to “work” for the things that they want and don’t take everything for granted.