For the past 9 years I have traveled with my six dogs. I always call ahead for reservations and have been refused only a few times, generally by any campground with the word "Resort" in its name that limits the number to 2, unless business is really slow and they make an exception. Most campgrounds don't mind the quantity as long as they don't bark and disturb others and are picked up after. I do a lot of KOA campgrounds because pet quantity is never a problem and I can always count on a pull thru site for the night. Plan ahead and you won't have any problem.