Their life wouldn't be so flipped upside down by one doctor appointment or one parent teacher conference if Jenn was capable of handing ANYTHING on her own. Having raised two children, I can think of a handful of times that my husband and I both attended a doctor's appointment for our kids. It's just not necessary. I don't even think my husband could name my kids' doctors through the years or could even say which specialist doctors they've had to visit throughout their childhood, and there are many. Not because he's a terrible person, he's a wonderful father...it just isn't necessary to make an appointment an all day family affair. I would, of course, debrief him on the appointment when he got home, but we don't both need to be there. I'm a capable adult. Often, I took one kid to an appointment and he took the other one to school/picked up/watched them.
Another pro tip for you Bojos: A secret to successfully raising two children is dividing and conquering. This will never be able to happen in your family unless Jenn gets the help that she clearly, so desperately needs and gets her shit together. You were irresponsible to have two children living in the situation that you do.