I wear size 10 and I ride mid-wide or wides. Why not? More float, more stability, no toe/heel drag EVER, and definitely no noticeable difference in how it rides no matter what anyone tries to tell you.
It's the specs that changes your ride, the most important being Contact Length, Effective Edge, and Sidecut Radius... the overall length of the board being relatively unimportant at all.
You really have to check into the specs of the width yourself, and not listen to if the company calls it a regular width or mid or wide, or whatever. (Some mids are actually regular or slim, some regulars are actually mids, some wides are actually mids but most are actually wide.. confusing I know). Here's some baseline numbers that are fairly common...
Regular = 249-254mm
Mid-Wide = 254-258mm
Wide = 258-265mm
(less than 249 is probably a girls board, and you don't really see anything wider than 26.5cm)
I'm assuming he'll be doing mainly beginner-intermediate freeriding at Sunshine & Louise, with the odd trip to other hills (The Horse & Revy of course).
Something around 158-163cm should be mint, with a minimum waist width of 252mm, and a mid-stiff flex due to his weight and riding style. Probably a directional-twin board, but I only ride twins now. Don't bother with a purely directional board.