Myself and ten year old needing advice

I was hoping to receive some advice from you all. And thankyou in advance for your time. My son is ten (11 in a couple of months). he has just finished with his end of year play at school in which he was chosen by the staff to help out in the younger childrens play (he's dependable in this way) he is basically chosen for the leads every year. His teachers, and as I have been told over the years also the members of our small town are surprised I havent put him into a 'Company'. To be honest, I do not know anything about theatre nor where to begin. He did a year of ballet when he was little because he was so agile and loved to dance at home . He's been playing keyboard for many years which ironically has just gotten him kicked off the school band because he becomes bored with notes and prefers to play by ear.(he learnt Fur elise and recently Mozarts turkish march by ear) I dont' see the problem but in the music world that's apparently a problem.*shrugs* He's happy just doing his own thing. :) Now to the crux of it...........I do not recognise my boy when he acts, he becomes a completely different individual (kind of scary for a mother who's used to an introverted child) I'm a bit concerned about auditions and signing him up to an agency because he's so introverted that it comes across as quite rude and I'm afraid that it will go against him. (Does it go against children who are shy?) But give him a character and tell him what the story is and he's off and running. So how does it work in the theatre world? Is this common in children within the theatre world.? All I can say is that my child "will just die" (< ----- Yes I know, rather dramatic) if I don't allow him the oportunity to do something with his "talent?". I'd like to ask direct questions but unfortunetly I don't even know what questions to be asking. Any advice would be appreciated. Thank you meg.