There are several approaches, but they all depend on what you are able to do.
- You can build a wheelchair detector. Then the closest found face detection, that is also lateral to the wheelchair, will probably be related to the guy in the wheelchair. However I can imagine compositions where this does not work. Wheelchair detection is possible through OpenCV. I have done something similar with walking aids.
- You can do some kind of person (re)identification, and let the user define which users to ignore. Have a look at authentication problems if you go for this approach.
