Keep the 96% and the Wartortle and catch the rest on CD.
Are the stats of Hydro Cannon known?
Blastoise will not bevome relevant because they would need to make Hydro Cannon insanely powerful to compete with Gyarados, or even more so to compete with Kyogre. Other starters also learn Hydro Cannon and have better stats, so it would make them unbalanced...I would get maybe two for trading and an evolved shiny, or two shiny even.
So for trading: evolve as many as you can comfortably store.