Oliver and Sean would have played against each other for two years at Hogwarts, before Sean went on to play for Ireland. Sean certainly has a lot of respect for Oliver on the quidditch pitch, and would be rather friendly if they should run into each other. Sean doesn't really have a mean bone in his body, and treats most people like brothers or sisters.
Terence might make Sean a bit nervous, if he were to know the military background. He thinks soldiers are very brave, but hates the idea of going into actual combat. Of course, Sean could easily warm up to him if they were to have a chat.
I just decided that Sean's a bit of a Quake groupie, so YES, he definitely knows Aisling! And maybe has a bit of a crush on her, too. Probably wishes he would've realized it while they were in school together.
Not sure Sean & Zacharias have any reason to really interact, so that's fine.
Evan's definitely too young to know Sean from school. Unless Evan was at the '94 World Cup, I'm not sure he'd have a reason to know who Sean is. =)