If you use the assumption that you are not going to get any overnighter just looking for a quick stop then 30 amp service would be fine as you will be a destination campground instead. For overnight, I am going to find a campground close to the Interstate AND with 50 amp service.
Keep in mind that a 30 amp coach can make full use of a 50 amp plug but a 50 amp coach might be crippled by a 30 amp plug depending upon the weather. I suspect the cost difference of a new installation would be minimal and only installing 30 amp would be a mistake.