RC just sent out an email once you've boarded you won't be able to leave the ship and the terminal closes at 5 pm May 8th.
"While we’ll depart from Vancouver, British Columbia at 3:30 AM on Tuesday, we’ve been advised that due to Canada Border Services Agency regulations, the terminal will close at 5:00 PM on boarding day and will not reopen until after we depart. As a result, once guests have checked-in and boarded the ship, they will not be able to leave the ship and return. We’re sorry for any inconvenience caused by this."