lynzi,
The way it used to be before Magic Bands (and MB's shouldn't matter) is that they would pull up to the guard shack and tell the guard that they are here to see you (by name) in site number so-and-so which the guard would confirm that you are currently a guest and your parents have the right site number. He would tell them to drive up and park up around the check-in building or overflow lot and bus to your loop/site.
Of course, after your parents pull away from the shack, they can go wherever in reality. For example, when we've had guests I move my car up to the lot so they can drive down and park at my site. I try to follow the parking rules by keeping all vehicle wheels on the pavement and out of the road.
The only time outside visitors are a problem are in really busy times like Halloween Day when the Fort is bursting.
Have a great time with them.
Bama Ed