Go to Inside Catholic for all the how to's for running into a large family in public or dealing with people who are a bit overwhelmed when they see you out with your large family.
I laughed when people thought I had a large family with 4! I was so poorly treated in fact my husband did most every errand for me next pregnancy. I've had people back away like its contagious (only if you really love babies and are blessed with fertility), swear (never necessary) and yes ask if I know how that happens. I really wonder if all those people with 2.5 kids have only been intimate 2.5 times.
Now I have big kids so if I really need to go out by myself I can. But I still take everyone sometimes. Its a right of passage they all must experience. And to the dear nun, who was petrified about her nearing surgery at the dentist: I understand and yes I'm glad too God called you to your vocation.