It has been suggested that minors could get a reduced level of UBI to recognise that they are have less basic need. However it should certainly be high enough to get rid of child benefits.

Interestingly until recently Children in the UK got UBI in the form of family allowance (paid to the parents). x for first born, y for subsequent or something. The sweeping government cuts lead to it becoming means-tested and complicated.

One Conservative (sorry cannot find the quote) remarked that they spent theirs on Champangne, which caused horror in the press, but is money flowing into the economy at least...unlike tax benefits to land-owners