B.C. Day is Monday August 2, and as you probably suspected, buses, SkyTrain, and SeaBus will be running on a Sunday/Holiday schedule. West Coast Express operates no trains or TrainBus on Monday.
Remember that the whole transit system is a single zone on B.C. Day, so zone fares are not in effect! So you can buy a one zone ticket and ride all over.
Also, don’t forget our group ride offer: on Sundays and statutory holidays, you can use your FareCard to take five other riders with you for free. That means you can take either one more adult and up to four children with you, or up to five children. The offer applies to the Adult FareCard, West Coast Express 28-day Pass, or Annual Employer Transit Pass. (It doesn’t apply to Concession Passes, sadly.)