It’s like shooting ducks in a barrel

This is a mash up of “shooting fish in a barrel” (easy action with guaranteed success) and “all your ducks in a row” (getting everything in order), submitted by a loyal follower, the TruroTattler.   Given the enormous amount of google hits, this is a common malaphor, as ducks appear to be as easy a target as fish.  Also shooting mechanical ducks in a penny arcade shooting gallery is certainly playing on the mind in this one.