My son brought a young robin home...not sure what to do?

my son and his friends found a fledgling robin which they thought they were rescuing. I know they meant well but I know how fragile birds are, and I'm not sure what to do. The tree they found him near is very high up.... no branches until about 20 ft high. He can't fly abd It's dark now... Should I try to take care of him for the night? I don't think he is injured, only weak. I fed him a small amount of can catted food on a toothpick and a little bit of water with an eye dropper. What's the best thing to do? Thanks