A child suffering with UC would be heartbreaking. The thought of taking out the colon would also be hard, but I would also look at how resilient children are. They adapt to things much better then adults do. I would hope the removal could at least not involve an ostomy bag.
If my symptoms ever became to the point that they interfered with my quality of life I would have the surgery. I have been there and done that with a temp ostomy and it was not bad at all.