I could be in a minority here, but I think the RV Campground "industry" has not taken the time to fully understand and capitalize on the attraction of overnite camping at places like Walmart. McKinney is on a heavily traveled highway (US-75) for campers headed south for the winter and north for the summer. There aren't a lot of good places for them to stay for the night in and around McKinney. As a Boondocker Welcome Host I've had a lot of campers stop in for a night on their travels thru the area, and I'm one of the few BW Hosts in this area.
My suggestion would be to consider an option for over-nighters - maybe away from the rest of your sites, but with greatly reduced prices and possibly electric as an option. Having a common spot for dumping tanks and filling with fresh water for them would be nice too. How one would get the word out and advertise this would be a bit of a challenge, but I suspect that after a short time the word-of-mouth advertising would kick in.
