Many people look at my dog photographs and say "Oh my dog would NEVER stay still like that!". Honestly most dogs don't stay still like that. All I really need is a split second to get the picture and often that's all a dog will give me. So it's fine if your dog is energetic and excited. I'm completely used to that.
I often photograph rescue dogs who are up for adoption and they usually are nervous, confused and wondering what's going to happen to them next (poor sweet things). They frequently have come from difficult backgrounds and the last thing they are going to do is sit/stay. I typically keep them on leashes for their pictures and then I photoshop out the leash. The pictures always come out great!
So your dog will be fine. Bring him in and I'll get some awesome pictures! If for some reason things just don't work out, I'll refund your session fee. But honestly that's never happened.