Ref. No. 1076/41-271
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
It is not permissible for a Sunni Muslim girl to marry a Shia person whose believes are based on kufr. Children have to obey their parents and consider their will or opinion. In this way their future would be safe in-sha Allah.
And Allah knows best
Darul Uloom Waqf Deoband
This answer was collected from the official website of Darul Uloom Deoband Waqf. The institution is based in India and the answers are provided in accordance to the Hanafi Fiqh.