Do you have access to a fish farm that sells hybrid bluegill (HBG) that are 3"-5" long? Stocking smaller HBG will not work very well for survival of stockers. They (HBG 3"-5") would fit your goal and thrive much better than the catfish and transferred large bream from another water body. Young people are not so much concerned with size of fish as much as staying busy frequently catching fish and HBG will nicely fill that goal. HBG do not easily become hook shy similar to catfish.
For more information as to what HBG can be in a pond with pellet feeding read through this thread:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=256325#Post256325If you plan to use pellets to feed and grow the fish, I don't think I would add lime to increase the alkalinity. What would be the benefit of doing this? Others might know of a good reason for liming a pellet fed fish pond.
However if the kids catching pond is for some adults wanting big fish then catfish will fit into your plan.
