Apprently I missed this thread when it was first posted.

I think I'd start off with either the mice or the rats. Espeically with the rats, I would wait until you are sure that both bp's will take rats. Sometimes a bp will not take rats and will only take mice.

I'm assumiing you want to breed the balls as well? If you don't have more than a couple of snakes I really don't think it woudl be worth the time and effort to feed, clean and take care of the mice or rats (unless you have a good local place that you can sell feeders to, and will let you sell feeders to them).