Based on my experience, I've never seen Gampel complete filled for this event even after a remarkable season or an upcoming one with great promise. Correct me if I'm wrong on that.
With that said, the lower section does fill up quickly. Depending on how big your group is, you probably can find a couple seats together in the lower section if you get there a little early. I wouldn't come 2 hours beforehand, but do whatever you think is best.
I would not worry about not getting in at all, so take the 3 hour trip and enjoy. I plan on being there with my son and his friend. I wish they still held the blue & white scrimmage, but those days seem to be over.