Your son will report to Alumni Hall. Either Gates 1 or 3 will work. Gate 3 is physically closer to Alumni Hall. Many people park at the football stadium and take the bus, which comes in at Gate 8 and drops you off in front of Alumni Hall. If possible, I would go to the Yard the day before, walk around and get the lay of the land, so to speak. The report times are staggered every 15 minutes. My son didn't report until 9:15 a.m., so there was no point in getting there too early. If you do, you end up standing around outside Alumni Hall, with the plebes-to be getting nervous and the parents getting whatever.
Check out the map of the Yard which (I think) comes with the appointment package. If not, you can find it online.