Do you know that he's even still going to that group?
My own feeling is that you need this meeting for yourself, you know the reasons you need to go (and don't need to justify them to anyone), so you go. Period.
Even if he still goes there, if he's working a program he may have progressed to the point where it isn't an issue for him anymore. If you see him, smile and keep walking into the meeting room or the car, depending on whether you're coming and going. If the prospect of your attending the meeting upsets him THAT much, he can change meetings. There are more AA meetings than Al-Anon meetings available.
Just my thoughts.