You don’t have to plan from scratch. These rides pass close to Quathiaski Cove, mapped and written up by route publishers around BC. The full maps and turn-by-turns live on their sites.
Quadra Island— Let's Go Biking · 30 km ride, passing within a kilometre
4 Ferry Odyssey— Cross Canada Cycle Tour Society · 165 km route, passing within a kilometre
Getting there with a bike: province-wide buses, ferries, and shuttles are listed under Transport (some serving Quathiaski Cove may be listed there rather than here).