The Templeton twins have an idea

I picked this one out for a read-aloud book for my daughter. I didn't get too far into it before her older brother decided he wanted to sit in on the readings as well. The Templeton twins are 12-year-old John and Abigail. They have an inventor father named Elton. But then the evil Dean D. Dean (and his brother Dan D. Dean) try to steal credit for one of Elton's inventions and the twins become part of the plans of the evil Deans. The story is told by a “narrator” who refers to himself/herself a lot, makes a lot of snarky comments, and generally is highly self-regarded. Quick story with some humor in it and my kids ate it up.