I already posted that a while back in this thread. But just to recap:
Something like this:
This would sort of bridge formal and casual:
And for casual:
or slightly more dressed up:
So, in short big on the black leather you mentioned, not so much on the rest.
Oh, except for that silly sorting ceremony we have to do with the current 12 and 13 year olds, for that he'll just rent an upscale catering uniform and say that it was a catering job for this weird pre-teen party to any non-magical friends he might make.