@newmaroonmom Your son has been admitted to one of the greatest institutions of higher learning in the world. He has shown that he is fairly smart and I suspect he can probably figure out how to feed himself 
You shouldn’t need to worry about him. The University of Chicago has approximately 7000 undergrads and has been around for around 125 years. Assuming on average of about 1000/class over those 125 years, that’s around 125k who have had to find sustenance and I’ve not heard of a single instance of a UChicago student starving. There are other things to worry about, but whether or not a 18-20 year old male can find food shouldn’t be one of them, it is in his DNA.
All kidding aside though, if it is looking for people to celebrate Thanksgiving with, I think he should let it be known that he’s staying on campus. Maybe look for a church or other place of worship to become part of and I’m sure he’ll be taken in.