I speak as someone who teaches history at an “elite” university…we’d be delighted by those A-levels.
The issue with A-level range is that some A-levels are less traditionally academic than others (eg English Language; drama; etc., which are a little less good if you’re applying to Oxbridge/Russell Group than more traditionally academic subjects like history, English literature, etc.) So a combination of three academically rigorous A-levels like English, ancient history and modern history would be absolutely fine. Those ones would serve him very well for applying for courses or combinations of history, English, classical civilisation, classics ab initio, philosophy, and so on (even law).
I would always suggest students do the subjects they enjoy and are passionate about for A-level — if he wants to do those the double history A-levels, and is enthused by them, and this means he gets the best results possible, then why not!
The Grade 8 music is a nice thing to have, and it does technically come with UCAS points AFAIK; but at Oxbridge we ignore music exams. However, you’re right that it does show commitment and high learning potential, so it’s a good thing to put on the UCAS form nevertheless!