I am prime example of what people with Disabilities can do.I have an assistant full time , Gina who makes it possible for me to work . My legs dont work but my brain certainly does .It is nice that you want to treat your friend to a vacation , if he is in a wheelchair like I am you need to do some research.I have ms WHEN I TRAVEL I TAKE MY MANUAL WHEELCHAIR. It sucks to get to a foreign country and find out you cannot charge the battery packs, been there and done that 
There are situations where engineer is right too though ,I hate people who suck the system dry and say poor me .