runner's made some good points. this idealized view many have of children is fairly recent...I seem to recall reading that it was until maybe the 19th century or so that the current view of children (and marriage, and family...) began to take hold. a lot of it was rooted in economic shifts related to capitalism and industrialization, the rise of the middle class, the move away from the farm, etc.
now that I think about it that way....we're all born with the sin nature, kids included. many Christians believe that children who die before the 'age of accountability' are spared hell, but...
kids are often inquisitive. kids also require discipline and correction, which are also parts of the believer's walk with The Lord.