We took our boy at 9 months and 21 months. At 9 months, he was fearless and loved the characters - at 21 months, he loved them except when he was right next to them, then he got shy and buried his face in the nearest available object. We did three character meals and halfway through the second one, he got over it (after several pictures with his face pressed into the arm of the chair he was in!) and was fine being right next to them.
Even when he was shy, though, he always enjoyed watching them as long as they weren't paying attention to him in particular.