I dont really know someone who is disabled and does aikido, but,
I do remember once, we had one of our big international summer schools and there was someone who was disabled there.
She was sitting at the end of the mat, as she was not able to use her legs ( I think there was some mental illness also). and people would go and train with her and she throughily enjoyed it.
I practiced with her myself, it was great to see the smile on her face, yes the technique obviously was not going to be too effective. But, she was enjoying it thoughrily, and for me that is the whole point. I do aikido because I love it, and for me training with someone else who loves aikido and gets enjoyment out of aikido feels alot better than training with someone who technically is excellent, but doesnt have that glint in there eye that says "yes! this is what it is all about"
I have also heard of aikido being taught to people in wheel chairs, but i have not witnessed it.
Love and all inclusive training