As rude as it may be I would rather them talk/text before the drive. I often have parents sitting in my driveway as well. I find it more annoying when they do it at pickup and we are outside playing and they sit in their vehicle on the phone before getting their child. Child is anxious to see mom but mom sits in driveway on phone for 5-10 minutes!!!

I would just put a request in your monthly newsletter asking parents to limit their time parked in your driveway for other parents picking up and dropping off.