Right across Highway 11 is Kahshe Lake
There is a public launch by Rockhaven Marina and pretty sure you can park at Rockhaven for a fee
note Kahshe is known for its rocks so if you do head out not a bad idea to check a map and or chat w folks at Rockhaven
Launch out of Honey Harbour, go tour Gbay then come back. A half day on the Severn Sounds like a lot of work and there will be a crapload of boat traffic.