Disabling Achievements and Trophies while using cheats is absolutely the right thing to do. I do not agree with disabling the save function though. You reversed this decision for the first Red Dead Redemption so please do the same for this one. I think this would make a great deal of people happy.
Please enable saves while using cheats like you did with RDR 1. I absolutely agree with disabling Trophies or Achievements while using cheats or any kind of stat ranking, but some people like myself just like to sit back and enjoy the game for it's story and gameplay and not for a challenge. The challenge will come in the multiplayer when it's released.