It's not clear (unless I missed something) if there is an additional charge for 'Passengers' but the total price is detailed as being for car + driver(s) so there does not appear to be a charge for additional drivers, therefore I would assume the same for passengers.
I expect you will be able to sign on as a passenger at any time as there is usually someone around in the Jackie Stewart suite.
Drivers (+ Guest) do get lunch
DRIVER Briefing is at 0830