Vancouver Island's a big place... Victoria area or Nanaimo? If it's a large boat that will be limiting too.. In Southern BC I'd say Shelter Island, a few miles up the river from Steveston will be your best bet, big lifts and lots of space with almost certainly the lowest fees.
On the island, not sure, but Nanaimo has a few on Newcastle Channel including a serious marine ways if no one has a large travel lift there.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"