I understand the concern (Father of 4). I think the reaction will be quite positive if the outfit is put together well. Spend a bit of time browsing the pics in the sections here to get a feel for putting together a nice outfit.

Button down shirt
Tie
Waist coat (optional)
Belt
Sporran
Kilt Hose
Dress Shoes

This outfit will give a very nice appearance that is virtually unmistakably Scots and should be received very well.

I know it's a risk, but I say if he's confident enough in himself and his peers, this could be a great time for him and a great example to many.