Remember that Kyogre outclasses other water mons already at level 30 which doesn't take that much candy. At the moment it isn't that necessary to have lots of good water attackers though, so I would just hold onto them.
As for Ray, with dragon moves it is an upgrade over Dragonite but not that big of a one. Then again, what do you need the flying moves Ray for either?
Verdict: Hold your rare candy. Unless you are extremely pressed for bag space, there isn't any reason to commit now when you don't know which one you'll need first.