Yep keep it simple.

A child should receive a UBI as well. It should go to the parent with whom the child is living with most of the time. This can be monitored with existing tax databases, so it would be difficult for both parents to claim the child's UBI. If they can't come to agreement, then a judge will decide.

As I have said before, start a UBI on the small side, maybe $200 a month. Slowly increase with time. As the increases occur, other social programs can be modified and later dismantled.