Minors income from US with expenses paid to parents

Can anyone assist on the tax treatment of a UK 4 year old who has received income from appearing on TV in US.  In accordance with US laws part of this income has been put straight into a trust fund, at what stage does this become taxable?

Also the parents have received travelling expenses to accompany their child, how is this declared to HMRC as there would be no profit in this regard but one of the parent's has received compensation for loss of earnings, which I would have thought was taxable.

Any advise would be appreciate as HMRC website seems to always steer me towards foreign entertainers

Jill.