Learning disability child applying for citizenship

I have a 15 year old autistic child. We are planning to apply for GV as a family (myself, wife and him). Although we should be able to fulfill most criteria under real estate investment path, I was wondering what happens if my son is not able to clear the Portuguese language test at the time of applying for citizenship. He will be 20 years old at that time and would have crossed the threshold of 18 year age. Can we expect any relaxation to the language clause under humanitarian/ exceptional case like his?