fairlise tam and boys long socks

I think the link is fairisle tam (beginners). My dearest oldest friend in the UK started this and finished it within a week and it was her first ever knitting project.

Oh does anyone know for a good long sock pattern for a 7 year old boy (he likes to wear boots and his short socks keep falling down over his heels). Also could I get away with using wool or should I make it a wool/nylon mix.