First, are they going to let you in with him? My father was not able to go into my mother's appointments recently even though she has early stage dementia.
Second, when we received our vaccine this last week, one of us went in the office and checked in. Then they told us to wait in the car until they were ready for us. They texted us to come in and we went straight to a room. I felt like our exposure was minimal. It's possible that they might have a similar setup, so call to find out if you can.
Finally, regarding N95s, they aren't perfect, but they're really good. It's likely the healthcare workers will be wearing them. If y'all are also wearing them, your protection increases.
Good luck!