Has to be Prince Edward Island
I'd head back and do Prince Edward Island again. We're thinking of getting a tandem and I'd love to do it that way.
When we went, there was no bridge and so the roads might be a bit more crowded during the main season. We went after Labor Day in 1990 and it was fabulous: friendly folks; more varied terrain than you'd expect; and just lovely quiet places to cycle (we stayed off the Trans Canada highway whenever possible--and it's very possible). We got a big kick out of staying in B&B's as well.
Glad you asked; I think I'll put a bug in my wife's ear now!
J