While pets can stay with their families in a wide variety of pets welcome accommodation, there are usually restrictions - especially when it comes to dogs. Dogs vary so widely in size that many dogs welcome hotels will have a pet policy about what types of pets can stay in their units.
Sometimes pets can stay in rooms unattended, provided they are crated and an emergency / cell phone number is left at the front desk. But if your dog is prone to barking or crying, or is anxious in new surroundings, it's not a good idea to leave him alone in the room even if it's allowed. A whining or barking dog disturbs other guests, and it's stressful for the poor dog too.