Your daughter needs to know why he will no longer be present or why he is no longer seeing him. The first step you should take is to let her know that you are no longer in a relationship with him. She will ask for the reason which you should provide to save her from thinking that her disability contributed to him leaving the two of you.
You will need to prepare your daughter psychologically for what you will tell her and being careful in the choice of words you use. She shouldn't think that her situation led to him leaving the two of you.
Should let him say goodbye to your daughter? Yes. The reason is to provide your daughter with peace of mind that her situation haft nothing to do with him leaving you.
You will have to talk with him on how to approach the subject to your daughter. After you have agreed, be the first one to let her know.
If he doesn't say goodbye to her, you will have to provide your daughter with a lot of convincing that her situation didn't lead to him leaving you.