We stumbled across The Magic Tree House series
when we got a single CD of the author reading “Dingos at Dinnertime” and listened to it, oh, maybe 800 times in the car. The kids love it and Grandma was kind enough to send us 8 entire stories on CD, plus the first four books. They meet our criteria of interesting stories, the two main characters (Jack and Annie) are nice normal seeming kids that I don’t mind my kids emulating, and there are even some good facts and learning to be had from the books. They’re chapter books, but they’re short so even my almost 3 year old can pay attention for an entire story. And, for the collector in all of us, there are over 40 books written so far.