I'm not sure about the perches and toys, I just change them around when I feel like it. I don't change the perches around too often, but toys I change around often.

I feed my cockatiels zupreem pellets and parakeet seed. I keep a seperate bowl of each in their cage at all times. They don't like the banana pellets in the zupreem mix , actually I've yet to meet a cockatiel that does. I'm sure Dawn will take to it just fine. My cockatiels are all rescues and when I got them they all took the change without any problem.