Govenor: It's been 7 years since my kid had her grad but the standard grad was back then a parade, atta boys and girls presentations, march past and salute and then turning in their weapons (that can take an incredibly long time so be patient). Usually there is a reception to follow for family and friends. Good idea for you to arrive before your kid and secure some food for them as that tends to disappear very quickly and for those left to secure the weapons, they do get there last.
Timings will be given to your son to pass on to you.
We stayed at a hotel in Barrie (IIRC, it was the Holiday Inn) and it takes about 25 mins to drive in. Give yourself another 20 mins to find a parking space and get to the parade square and seated.
One bit of caution, as much as you are happy to see your child and vice versa, don't be surprized if they make a choice to want to spend time with their buds instead of you. Your son may not want to hang out with you or go to dinner. Don't take it as an affront, but rather it's all about who they have become. The CF is their family now and these people who they have just shared some incredibly hard and fun times with are as important to them as you are if not more so. They won't leave anyone behind that doesn't have their family there to take them out to celebrate.
Enjoy the day. The day my daughter graduated is right up there in her life moments that as a parent, I'm glad to have been able to witness.