URGENT: 10 Points? Please Help!?

Well see, tomorrow, a good friend is coming to see me where i play table-tennis (It's a coaching class) .The opportunity to see him is very rare, as he studies in my brother's college, Plus, he's amazing! :-) Well, I can't afford not to see him tomorrow, as I'm going for my vacations tomorrow. And he's going to Malaysia forever, as his college gets over tomorrow (He's in his final year) . So the problem is the timings of the class, and the coach's son. the class starts at 4:30 and ends at around 6:45. I can either ask him to come at 4:15 or either come at 6:20ish directly. The coach is a really nice guy, but his son is not that good. He comments on us, Changes our style of playing to awful techniques, and literally ruins our game, and has favorites. I'm not one of his favorites. I don't like him, and i show that. I don't act really formal. I talk as though that guy was just some guy, like "Oh yeah, That's completely insane. Impossible. Yeah right. I dunno,how am i supposed to know. " So point is, I don't like that son. So my dad comes to pick me up at 6:45. And he wouldn't want me meeting friends here. Either I go at 4, he'll come by 25 (The friend) and i talk to him for 15 minutes. Or otherwise i call my dad and tell him to come at 7. so that from 45 to 7 i talk to my friend. P.S. How to tell a guy who's 10 years older than you that you're going to miss him a lot? Because he's kind of shy. :S Please Help. How do i get that coach out of the way?! Because, if my friend comes in between the class, The coach won't allow me to meet him!