Agree with meggles that this totally depends on your grandson. If he is a high stamina night owl, then MHP might be lots of fun for him. Otherwise, it will be an exhausting day for him with loads of stimulus. How does he do with meeting characters or with people in costumes? Characters may be fine in daylight, but scary at night. We've seen lots of little ones do poorly at the parties, which frustrated the parents ("Stop crying! I paid tons of money for these party tickets!"). And there have been complaints on this board from parents who had to leave before the parade and fireworks because the little ones just couldn't stay awake. On the other hand, some little ones do surprisingly well with the late hours. From your signature, it looks like this won't be your only trip to DLR. So if it seems like MHP might be too much for your grandson this year, you can always plan another trip when he's older.