I'm sure I'm not the only one thinking that wherever you do your trial lesson, it should be 'fun' (if your brother likes that kind of thing). So I'd choose the location he does it based on convenience rather than the possibility that he may want to carry on to be a professional pilot!
Even if the cost of the trial lesson was wasted (which it wouldn't be - if he's never flown before he will have half an hour of sensory overload wherever he does it), in the great scheme of things, it's diddly squat.
Let's hope he doesn't hate it....