My son wants to see grandson but I'd prefer to not be on the floor, are under 21 allowed in the balcony with an adult?

yes

I know your busy so I appreciate you taking the time to answer questions. The grandson show on Sept 29th just shows general admission, would tickets be available at the door or at all for the balcony? My son wants to see the show he's 14 and I'm 50 I'd just rather not be on the floor. Thank you.

Depends on the show. Sometimes they close it off completely