Depending on your state, Medicaid sucks big time or a little. California and New Mexico, for example, have run out of money to fund this kind of "insurance". I now have to tell my patients that I can only perform one filling per tooth every three years but, if they get more decay, Medicaid will happily underpay me to extract it. Medical treatments aren't much better.
My experience isn't exactly personal, but I work in Patient Financial Services for 2 hospitals, one of which is the only trauma center in the Northwest and the other is a BIG teaching hospital and affiliated with Seattle Cancer Care Alliance.
Both hospitals have active charity programs and take patients with Medicaid/DSHS. Everyone gets the same care. Period. But what is really interesting is that for patients with this coverage, we will write off any balance leftover after Medicaid pays. As I understand it, this is the law, but not well known among the general public. Hospital based clinics are probably more likely to follow through on this because they have bigger billing departments and are more closely monitored.
You may have to be an advocate for him, but your son should be able to get good care. Keep us informed. I will keep positive thoughts for you both.