How early should we arrive for a party of 8 if we want to eat at 5?

430,just to get in line. I'd call ahead just to see if they can accommodate you.

They open around that time so shouldn't be too bad.

At 5

Normally they can seat relatively quickly, but call them and give them a heads up. They are very accommodating.

They open at 5 pm, so the earlier the better

I would suggest 4:45, so you're in line when they open.