1)
Why is this repeated? Verses 6,7 already bring essentially this question and answer!
1.
Radak: Here, children who will be born later ask.
2.
Alshich: Here, your grandchildren will ask.
3.
Malbim: Here, later generations ask.
2)
Why does it say that your children will ask their fathers?
1.
Alshich: Your children really means your grandchildren.