The recipe looks OK. I would skip the cascade at the end if you plan to add fruit.
Blueberries are notoriously difficult to extract the flavor from. I would say you probably ought to use double whatever you had in mind. I use fresh fruit, that I thoroughly clean and inspect, discarding any damaged or rotting pieces. For blackberries/raspberries/blueberries, I "distress" the fruit a bit (basically pound on it with a sanitized blunt object) and put it in a sealed sanitized container to freeze overnight before racking onto it in secondary. I personally put my fruit in a nylon mesh bag (hops bag, usually) and tie it up really tight so as to make it easier to rack without getting little bits of fruit in the beer, as well as eaiser clean up when I'm done, but that only works if you're fermenting in buckets.