Hes a fashion refusnik but we have a formal garden party thing coming up and I've persuaded him to wear beige chino- type trousers and a navy linen jacket. What shirt though? He's a big, big man - think tall hefty (and comfortably portly) rugby type, but of a tum. And what cour shoes? Black or brown Cheers in advance.
Most definitely brown shoes. Black shoes are a big no no with beige chinos and navy jacket - can't emphasise this strongly enough.
Gingham and fine check (i.e. white with coloured cris-cross lines) shirts are really "in" for men this year and might suit him if he has a bit of a tum. My posh FIL regularly wears chinos and navy blazer with a fab pale blue gingham shirt- and he has a big tum! As the jacket is linen a muted/pale shirt colour/pattern would look best IMO eg pale blue/pale yellow/pale pink/pale lilac.
If you want a really safe option just go for a plain white linen mix shirt and then could always add a hanky to the jacket pocket to add a splash of colour.
Get a classic fit shirt from a traditional shirt shop to ensure not too trendy/bad quality/strange collars or alternatively see what they've got in M&S.