Looks like I'm in the minority here, but we went last year when my son was 5, and he LOVED the Agent P experience. I don't really recall there being much reading, as the "F.O.N.E." he was given spoke the directions right to him. There may have been a few times when I had to look at the FONE and read what it said, but mostly, he listened and led us off to find the next stop. He loved having a mission to complete and searching through the different pavilions to find the right spot.
But then, he isn't a kid who loves to sit and color for more than a few moments at a time. He'd rather be up and moving, even on a busy day at Disney!