I really don't like when adults -- especially parents -- scare their children and laugh about it. Clearly these kids are totally terrified by the sight of the Grinch. Why would a parent include this intimidating mascot in a holiday photo when the kids react like this?
There are so many videos on the Internet where kids are scared of animals, insects, or whatever and the parents just sit back and laugh. There really is nothing funny about it. A fearful reaction from a child can leave a long-lasting scar and have some serious affects on their mental health.
Please don't put a child's safety in harm's way. If you know something is going to scare a child, pass on it. And the worse thing you can do is mock them by laughing. I know everyone wants to go viral with a cute kid video but there is nothing cute or funny about putting a child in a situation where they are uncomfortable or afraid. Nothing.