He was watching from a balcony. Probably the seats reserved for friends and family. Don't see why Kirk wouldn't give him one of his "tickets". Maybe Mom and Sam were there too.Pike knew of his dad. I don't think an actual meeting or relationship between G. Kirk and Pike is mentioned. All Pike did was challenge Kirk to join Starfleet and later make him first officer. It was OldSpock who pushed Kirk to take command of the Enterprise. As far as I know, Starfleet Command knows nothing of the other Jim Kirk or his background and it would not factor in their decision to make their Jim Kirk Captain of the Enterprise.
Spock Prime was at the ceremony where Kirk was promoted to Captain. I can't believe he had no input into Jim Kirk's fast track to command. Didn't exactly look like a public ceremony.
He looked to be the only one there. If you see others there let me know cause I completely missed them.