It seems like there hasn't been a really good childrens' movie in a while. Perhaps it's the lack of good ideas. For that reason, I'm submitting the following ideas for sequels that I think can reinvigorate some neglected franchises:
Babe: Pig in a Blanket -- After his adventures on the farm and in the city, Babe meets a sad demise as he is killed by a drunk hit-and-run driver. In an uplifting ending, he is still able to bring smiles to the faces of thousands of children.
The Bipolar Express -- A middle-aged man continues to believe that Santa Claus is real, insisting that he once rode on a "magical train" to the North Pole where he met elves and even Santa himself. When he begins to complain of auditory hallucinations, maintaining he can hear sleigh bells that nobody else can hear, he is committed to a mental institution for his own safety.
Honey, I Shrunk the Kids' College Fund -- A nerdish scientist foolishly invests his two childrens' college savings in Bernie Madoff's Ponzi scheme. Desperate to replace the money before his wife finds out the truth, he uses his technical skills to break into a bank. The robbery goes awry and turns into a siege that ends when he is shot and killed by a trigger-happy SWAT sniper. Fortunately, his widow is able to sue the city and the settlement is enough to ensure that the kids never need to work, so they don't bother going to college.