You don’t have to plan from scratch. These rides pass close to Tsawwassen, mapped and written up by route publishers around BC. The full maps and turn-by-turns live on their sites.
Vancouver Crossing Loop— Adventure Cycling Association · 503 km route, passing within a kilometre
Getting there with a bike: province-wide buses, ferries, and shuttles are listed under Transport (some serving Tsawwassen may be listed there rather than here).