We resolved the which pet to get? issue on Wednesday. After our class at the Y, we drove up to Just Pets in Tempe, and got the cutest, friendliest, and most adorable teddy bear hamster to ever exist. (I have no prior experience with hamsters, but this one is great.) Jarod at Just Pets is awesome; he really knows all the animals there and chose this one particularly for DD, since it is very well socialized and therefore good for little girls.
Then we went to PetSmart and bought all the things the hamster needs, like a habitat and a ball to roll around in, and food and bedding and a tube to sleep in, all that good stuff. Jarod actively dissuaded us from buying that stuff from him, as that's not really their thing: they're really into the animals, not so much the stuff. I recommend anyone looking for any kind of pet in the Phoenix-south area to check them out.
DD named her Frederica, and calls her Freddie for short. She's reading a book about a golden hamster named Freddy, so that's where that name came from. Her first day home, Freddie spent most of the time in her tube, freaking out (I suspect.) But she discovered the wheel in her cage and loves it, and loves rolling around the house in her little plastic ball. We put the cats in a room with the door closed when we let Freddie out -- the temptation to play hockey with the hamster ball is much too strong for the cats to resist.
I never had pets growing up, and all of my pet experience until this week was with cats. It's amazing how one little hamster can be so solidly wedged in my heart in the space of two days.