Iggette,I am so sorry for your cats,I bet they wish he was gone
I hope they don't get too stressed out by this BIG change..
I've never had cats getting used to a new dog,I've had it the other way around and my dog was like Sadie and she readily accepted the cats.
I know you are not going to give up on Buddy and I wish you and your cats all the best,it's a good thing Ursa accepted him with no problem...