We have a permanent site right next to the playground at our CG. On the opposite side there is a short foot bridge that goes over into an area that a lot of weekend campers use. I can't count the number of times people would step off the bridge and then head straight for the playground instead of walking around on road like any decent person would do.
Sounds like you need some stakes and plastic chain. Make a small "fence" with so they can SEE they shouldn't walk there.
1988 Coleman Sequoia - popup (1987-2007)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10