Like you, I have two cats and my older one is, um, rather set in his ways and gets feisty when Sweep gets too close. She's been here almost two years though, and he's never drawn blood or even aimed for her face. It's more of a spit/hiss/warning swipe from the couch as she's passing by. She might bark back at him when he does that (he gets her on the butt and I think it surprises her), but nothing's ever escalated beyond that. So I wouldn't worry too much about that aspect of it, though of course that's easy for me to say now! It took us a year and a half before we left Sweep loose in the house with the cats when we weren't here. (We were lucky in that she has always crated well.) That said, we did leave her loose overnight much sooner. The cats are on the bed with us, and Sweep's bed is in the bedroom but not in the traffic path where they'd have to pass her to get to food/litter. We have never had any overnight incidents (knock on wood). If you have the room for such a setup, I'd try leaving Aiden out on his own bed in the bedroom with his muzzle on and also let your cats have their normal routine as much as possible.
By the way, I think that's a good rule of thumb re: dog bed placement in general: keep it somewhere where Aiden can observe the goings-on but isn't "trapped" in a corner, and likewise somewhere out of the human and feline traffic flow. Should help keep the peace.