I would stand far away from coughing people, or even people with colds when your babe is less than 4 months. The distance you need to stand is something you will have to look up (google airborne/droplet transmission distance) and see what you come up with. The biggest I have seen is 7 feet, so that is the number I would do…but please check for yourself. My glance was cursory. Some research seemed to show the closer you were to someone with pertussis and the longer you were with them seemed to increase the liklihood of getting pertussis - so short outings where you keep your distance from the masses.
Carry your baby. Most wraps are so complicated looking that most people do not offer to hold the baby when it is in a wrap, as it is such a PITA to get on and off.
If you do well child visits, consider going first thing in the morning, before the sickies populate the waiting room. Don't bring your older child if at all possible and avoid touching the toys, etc.
I would also work on teaching your older child good cough and hand hygeine (maybe she is already great in this area, but I know many kids need frequent reminders).
There is a battle of two wolves inside us. One is good and the other is evil. The wolf that wins is the one you feed.
Book and herb loving mama to 2 teens and one young adult.