Grandstand information Spa 6 hours.

Hello All.
Going to Spa for the WEC, 6 hours with my son, first ever visit to the track.
Got my entrance tickets sorted but have a question regarding grandstands.
Unless im looking on the wrong part of the site, I can see no information about the stands?
Are these extra or is it like Silverstone used to be and Grandstands are free on a first come basis?
Any help, I would be very grateful.
Thanks.