Here's an article about Peter's Oct. 7, 2010 free children's concert at The Monkey And The Rat which is owned by his son Christopher.   DK if the accompanying photo is current, but in it he doesn't look different, age-wise, from most of the other folkie guys (or other guys) I know who are in the 65-75 y o range.   But if he's lost a lot of weight recenty, maybe from a cancer treatment, that might well make his face look older.