I'm more worried about the words "Rick Warren" it can be kinda cultish. Sorry dog, I just had to say it.
Wasn't small groups invented by Warren? I've seen good and bad from them. Some of the small groups I was in when at a PD church met in homes and started using any materials they wanted, began drinking alcohol and really got out of hand with no accountability. And anyone was allowed to teach/lead.
Small groups started in Acts 2...unless you believe thousands went from home to home.