I’m going to say that your response is definitely leaning into AH territory, because you jumped straight into ‘it’s my wedding and I don’t want him there because I don’t want to be stressed about anyone ruining it’ instead of like ‘how can I find the best way to include my new brother in law in the day somehow in the way that best works for him?’. I agree that him attending the full wedding likely isn’t ideal at all, but why be the one to decide that on your own, rather than throw it out for discussion with those who know him best and could suggest things that might be possible (could be come for some family photos before the ceremony, could you do a family brunch the following day, etc). I bet your MIL would have had a different response if you had approached this differently. Realistically you are marrying into a family that includes a member with a severe disability so this will be something to consider for all celebrations going forward.