I was with my daughter for a clinic appointment today. No issues with my being there with her.
An elderly couple came in while we were in the waiting room and the check in nurse said they were limited to the patient only. The wife said something to the effect of "I need to be there with him" and that was the end of the conversation. Both checked in and waited for his appointment.
I'm sure that all that is needed Paul. Just politely tell them that you need to be at the appointment. No need to go pissing in the parking lot.