check out my blogroll at
www.familyonbikes.org/blog for lots of families out there touring with kids! We started touring with our boys when they were 7, so I have no direct suggestions for little ones but there are plenty of families out there with them.
The pedouins (
www.pedouins.com) have cycled from Kentucky to Alaska on a bicycle built for five with three small children. They are almost at their destination of Fairbanks.
One thing you will find is that you'll travel differently with kids, but it's a fantastic experience!