Welcome to the Rat Shack! I can't wait to see pictures of your girls! Have you decided on names yet? I agree that a double CN is going to be HUGE for just two rats. I actually just got the single CN a week ago and it's SO big for my two males! They love it, though. You can see some pictures on my blog to compare the size. A double isn't totally necessary for only a few rats, but I'm sure they would love all that space! The CN is really an amazing cage, though. I was using a Super Pet Deluxe Cage for Exotics for the first few months that I had my rats. It was okay, but once the CN arrived I realized how much I had hated reaching into the cage to clean the shelves. With the CN, you can open the doors that make up the front of the cage, and you're practically in the cage yourself! Cleaning is less of a hassle now, and I do it more often which makes both me and the rats happier!
I also have Oxbow Regal Rat diet, but the packaging says "for adult rats only" so right now I am feeding Mazuri to my males until I can get a big bag of Harlan Teklad ordered. I also give my boys fresh vegetables every day as part of their diet, and as for treats I give them fresh fruits, cereal (usually whole grain flakes), yogurt, Nature's Animal all natural dog biscuits (comes in chicken flavor, lamb and rice flavor, peanut butter, etc.), Wellness Wellbars: Yogurt, Apples, & Bananas flavor, Zukes Mini Naturals dog treats, etc. I don't give treats very often because I don't want my boys to become overweight, but those are the different types of treats I feed them. I never thought of giving them dog treats before, but the dog trainer at my work (a family-owned pet supply store) gave Eli a Zukes treat and he went nuts for it! The Nature's Animal dog biscuits are all natural and great for them to gnaw on. A lot of people feed baby food as a treat, too, but I've never done that. Peas are excellent treats, too, and can also be fun to fish out of a bowl of water!