Smiles for Grandpa

We went to a park on Sunday with my parents. There were some pretty pillars, so I thought I'd take a quick photo of the kids before letting them play on the swings and slides. I'm a mean mom, I know. I begged and begged for a smile (or even a glance in my general direction) and this is the best I got:

Suddenly, Grandpa showed up by my side and made a silly face. Those kids lost it. I could not believe how hard they laughed.

Seriously? Why can't they smile/laugh like that for me? So it's official, Grandpa needs to follow me around whenever I bring out the camera.