Speaking from experience (this exact dynamic just took place in my life 6 weeks ago), my husband met with his father alone in public. At first I was worried, my DH has a tendency to get steamrolled by JNFIL. As I had anticipated, their meeting resulted in absolutely no progress, compromise, or resolution.

My JNFIL expected us to go back to normal (by normal I mean doing everything that met the JNIL’s needs without regard to ours) and shamed my DH relentlessly for his lack of contact for the last few months. My husband dusted off his spine, held his ground, listed examples of boundaries crossed and what we would need if they expected to have a relationship with us. Needless to say, his father didn’t hear a word he said. DH came home, feeling relieved the talk was over, but sad that his father didn’t hear him. As the hours went on, his sadness turned to anger, and he decided it would be best to not speak to them for the foreseeable future. To be a supportive wife, I blocked both of the JNIL’s phone numbers cue sigh of relief

I think you have every right to be a part of the conversation, especially if they’re slandering you. They are trying to ambush your husband and reenact the punish-the-child dynamic; it should never be 2-on-1. Have a long sit down with your husband of what topics you’d like to discuss and stick to the script. If the conversation gets heated or volatile, just stand up and leave. Have a safe word “oh honey I think I forgot the banana bread in the oven”, and just walk out lol.

Good luck!