I do think its altruistic - just not amazing. Its not his only guitar - and I expect he will gain as much from the experience as the children.
Most people in their lives contribute to the wider society in some way in time or money. Its what we as humans do.
My local school regularly has students do a VSO type activity, where the students themselves raise the money -I know about it as I was asked to do a dance for them and the Dartford folk club provided a raffle prize. Its a seriously worthwhile activity - but normal people to do.
FloraG.