For the elevation of his soul, please recite at least once a day the "asher yatzar" bracha by reading it from the text (as opposed to saying it by heart).
This is especially meaningful because of their disabilities.
Anything done in his merit should be l'ilui nishmat Yisroel ben Binyomin.
His existence added great merit to the world, and his passing remains a tremendous loss.
Here is a moving poem by Nechumelle Jacobs in honor of her husband's yahrtzeit: