If you want to see both, you will need to stand over near Monsters Cafe to see everything. Problem is once the concert starts and the parade ends, lots of people will be walking in front of you.
My suggestion is to watch the parade by Amity/San Francisco,basically close to where it begins on the Disaster side of the street and after it passes you,race over to the concert area staying on that side of the street.You could even walk with the parade and catch some more beads.