If you are plannig on separating, you may want to see who had adopted which pets and find a way to compromise about w whom the pets will end up. It is a very difficult spot to be in. Perhaps you can think of some pros and cons to present him with in regard to splitting the pets and also how that would affect you.
See if he would be willing to get some mediation so the two of you can at least be happier and more peaceful. Don't give up either.