Yeah, Riley loves it. I don't yell 'boo' at him, instead it's the 'I'm-gonna-get-you!' game, which can be played inside or out. Mick and Murph don't grasp the concept and just look hurt that I'd try to chase them. On the other hand, Murph is perfectly happy to help me stalk Riley, then we both rush him.
Dad will play with Riley, too (there's more space to run at Grandma/Grandpa's house). I really need to get a photo of Dad hiding behind a chair.