I had a camposite request this and I think it could be amazing.

A print to order sign (super cheap) maybe in a plastic paper with our logo and QR code to the specific booking page of campsite, that way people don't have to go in and ask (many don't) and they could just see the sign with "BOOK NOW" and our logo plus QR code. If every campsite had one we could catch all the people that are looking for a campsite to stay in for the night and could convert very well for a very low investment, plus our logo would be everywhere and it can be hanged on front gates etc.