Here's a story for you. I gave my son whooping cough at 2 months old. He had just gotten the first vaccine, but it's not effective until after the third dose at 6 mos. Anywho, I certainly wasn't held or touched by the stranger out in public when I contracted whooping cough. It's respiratory, so it's passed via the air. You don't have to be particularly close to anyone to get exposed. I went from 0 to pneumonia in 4 days. I was sicker than I have ever been as an adult (mono might have been worse, but not by much) for two solid weeks. I started feeling a little sick on Friday night, diagnosed with pneumonia Tuesday (would have gone to the doc Monday, but it was a holiday) and given antibiotics, Wednesday evening baby started coughing, thursday he was at the doctor's and given antibiotics. They also tested him for whooping cough just in case. Friday, my husband was sick and given antibiotics. Saturday, the pedi called with the results of his positive whooping cough test and to make sure everyone in the house was being treated with the right antibiotics (thankfully we were). And advised us to notify anyone we'd been in contact with. This led to my SIL, BIL and niece all having to take antibiotics because they stayed with us as I was getting sick. Best I can figure is about a 5 day incubation period too, before you start showing symptoms.
All adults should get the tdap vaccine if they haven't had the booster within the last year. They took the pertussis out of the adult vaccines many years ago and only recently have they put it back in. My vaccine was up to date, but I didn't realize they had taken the pertussis out, so I ended up being unprotected, and so did my husband. The county called after the positive test (reportable disease) and recommended that we get the vaccine after we felt better again anyway because they had been seeing instances of re-infection.
Listening to your newborn struggle to breathe while coughing and trying to cry but not being able to because of the coughing really sucks. The only reason he did so well and didn't have to be hospitalized is we were watching for it since I was so sick and caught it immediately. But he was still really sick. It took us two weeks each to feel better and months before the coughing really went away.
So, if those family members are too chicken sh*t to get a shot, they can't see the baby til after his 6 mos shots. Pertussis is extremely contagious and dangerous.