I strongly doubt they're pressuring their child to be normal : Eccentricity and 'being interesting' are cherished qualities in the UK. I'm guessing that what they're saying is that they're making sure he has 'space' so that when he wants to do ordinary stuff, and that there's no-one whispering in his ear that he needn't be interesting in playing football (soccer) because he's a genius with a higher calling.
Also, maybe the art thing is just a childhood phase, and that's Ok by them too.
From what I see from the people around me in my office, attitudes to children (and their education, aspirations, etc) are very different US vs UK.