In general, it's not expected that passengers will be driving and if this is something you require, make sure to indicate it in your trip description and to check with passengers that they are OK to drive before approving their booking.
If your passengers agree to driving, make sure that they have a valid driver's license and that your vehicle insurance covers them to drive.
If you are making a long trip like Calgary to Vancouver (1,000 km), make sure that you take plenty of breaks even if you are sharing the driving. We recommend breaks every 3h or 300 km to ensure you are well rested while driving.