Patience is a virtue

We learned today that Athens Clarke County likes in line far more than online when it comes to registering for county recreation department programs. Clara and Margaret and I started standing in line at 9:15 this morning, and finally left at 2:45 p.m., having secured one of three summer classes we were interested in. They didn't get into a puppet making session at the art center, nor an animal-centered one. But we did make a gymnastics program that Margaret will enjoy far more than Clara, I believe. M isn't as coordinated as Clara, but she enjoys being upside down and bouncing and spinning around.
The girls were great while we were waiting. Not any whining or complaining. We did manage to go to the potty twice, traveling there by elevator and then returning by the coolest of all, an escalator. Both girls knew what an escalator is from the book Corduroy, but had never been on one until today. It was so exciting for both of them. Clara insisted I hold both their hands, which I was happy to do. And this particular escalator was really really long.
A couple of times today, as the line crawled along, Clara lost sight of me. She panics when that happens, whereas Margaret is happy just to find a new friend and be on her way. I am torn between making them paranoid and having them be too friendly. I don't want them to be afraid of people, but I do want them to be cautious. To speak to my friends and acquaintances, but no one else. I'm not sure how to do this. In familiar places, like Publix, they expect everyone they meet to be kind and friendly. For the most part, other customers and those who work there are kind and friendly. But I have read and written stories about children being snatched from grocery stores.
WWPD? What would Peg do?