You can rent bikes right in Stanley Park, I know. Don't miss the huge great blue heron colony in Stanley Park right by the Park Service house on English Bay. Best restaurant in that English Bay neighborhood: the Banana Leaf (Malaysian). And re the cruise: definitely worth doing a side trip in Juneau to whale watch. We did this cruise four years ago, took the side trip, and got to spend an hour with a dozen humpback whales while they were bubble-net fishing. Truly awesome experience.
In August, the weather is likely to be great.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks