Well you have to take in consideration that the cats stick harder to their own habits so they are harder to convince to change their habits.
If you are located in North America, then the wet canned food for cats are the Innova Evo (www.evopet.com), Wellness (http://www.omhpet.com/), Wysong (www.wysong.net), or Azmira (www.azmira.com). The reason I recommend those is that the meat comes from human grade sources.
Don't worry about the vegetables and other additional ingredients found in those wet canned food. It's just that in nature, an wild cat might occasionally eat the predigested vegetables found in the stomach/intestines of the prey.
First take the step to switch your cats to wet canned food. When you fully switched your cats to the wet canned food then you can figure out the next step to switching to prey diet.