How early should I be there for Hawaii USS Arizona tour?

Since we will also do the PCC Luau that afternoon (bus pick up at 12:05
PM), we want to make sure that we could finish USS Arizona tour as
early as possible. I checked their website, the ticket is based on
first-come-first-serve. And the tour won't start untill 8 AM, although
the Visitor Center starts at 7:30 AM.
So how soon should we arrive there?
Since we don't have rental car, so what is the best alternative
transportation method?

Thanks a lot