My Grandparents are Secret Agents by Scott Christian Sava

Alyssa and Nicholas' grandparents are taking care of them for the weekend while their parents go to New York.  They're expecting to have fun with the grandparents, but they had no idea how exciting things were going to get!  It turns out that their charming old grandma and grandpa are actually secret agents, and Alyssa and Nicholas end up tagging along with them when an emergency case comes up.

This was cute and quick.  It was very simple and drawn with bold, bright colors.  Grandma and Grandpa are trying to stop the evil Purple Haze, who's trying to make it the 1960s again by stealing different components to make a time machine.  Alyssa and Nicholas take the news that their grandparents are fighting crime very well, and off they all go on their adventure!  Their grandparents provide the children with a robot dog to look after and protect them, and the robot dog ends up saving the day.

There wasn't a whole lot to it, but it was certainly fun and I think would be a great read for elementary students.  And we get to learn about how things aren't always what they appear, and that your old grandma might actually be a kick-ass crime fighter!