Have you tried putting a bit of the tuna in with the Felix to see if that tempts your cats into eating it?
I've known cats live until a ripe old age on dry food, as long as it's a "complete" food and they have access to plenty of water.
Otheriwse, yes, try raw meat. Chicken has a good amount of Taurine which is essential, but make sure they also have access to liver and other offal (kidney, heart, etc) and bone (if they have good teeth).
Without the bone, you'll need to add calcium additives. If they have their own teeth, start them on chicken ribs/wings/neck and soon they'll munch through bigger bones with no problem.
Look at giving them 80% meat, 10% bone, 5% liver and 5% other offal...and about the same amount as your normal wet food...you'll know if they're still hungry or leaving lots.
My two LOVE lamb but it's pricey over here, is lamb/mutton/goat affordable in Saudi? I know the Halal butchers here are pretty good.
Good luck.