You are correct. The best place, and the nearest parking is where you just described. It is situated above the Portal Family campsites, next to the closed gate that leads down to the campsites.
There is nothing closer. Depending on when you go and arrive, parking can be an issue.
Paul
Thanks!! I guess we'll try to get there early. If anything, we can drop the gear off and one person can park far away and walk up to the trailhead. Our target is late July.