Howdy @Jenn82 !
I hope this note find you well. While I don't have a dog I have given many rides to dogs on my NRS Thrive paddle board. In addition, I have two young kids that are often riding in front an in back of me. Each board we have has a weight rating associated with it. Several of the inflatable board we sell would work for you. Generally speaking, as the boards get longer, they accommodate more person, gear, dog, kid weight. In addition, the thickness of the board matters as well. I've also seen folks using old yoga mats as supplemental pads for dogs to avoid any paw scratches. All the best to you as you get out on the water this season!