I don't know how long ago you moved, but keep in mind that any move is a big adjustment for our pets. New places, new people, new smells - all at one time.
Has Callie been around children much in the past? If not, perhaps you should start off slowly, with just one child, preferably one who has been around animals before, and knows how to approach them. Keep it low key, and short. If all goes o.k., then gradually introduce her to more children.
I agree with Rachael about letting our babies off leash in a park with large dogs around. Just too dangerous for me to chance it. Also agree that you should not reinforce her fear by babying her. If she runs to you and you pick her up, and comfort her, she will probably associate the comforting with being afraid and think it is O.K. to be afraid.
I've been working diligently to socialize Jasmine, taking her with me anytime it's possible. My last chi was a rescue and had been mistreated, and was never comfortable around anyone other than family, and was terrified of other dogs and cats. I didn't want Jasmine to be that way, and she is making great progress. Just be patient and diligent in working with her. Some chis never learn to like children - that's just their nature I guess.
Just some suggestions - these are the things that are working for me. God luck.