I found there you can't bring pets with Sims to volenteer.

RoseyaSimi4

I made a Sim that is living a rich life. I about to send her to volenteer for some reputation to be famous. She has a dog that I want him to go with her. I can't bring him as if he's part of it too or in his arms that never lasts when their at home, I can't even simtagram the pet in her arms. Being in her arms would make a great picture. She just needs to draw the camera like a selfy.