copyPixels lag issue

I'm currently working on a mobile app wich is supposed to be a store of interactive books for kids. These books, being interactive, cannot be loaded SWFs as the app will have to work in both iOS and android, and as you may know that simply doesn't work in iOS (apple always HAS to be different -.-). Having that in mind I moved to create a my own AssetLoader system that will get urls from an xml file, load everything and finally display it. Sounds easy right? Well, it is. The major problem here is the animations: they are 2 files (a png spritesheet and a json) wich are parsed using this library, but the tiles can be small, medium, big, wathever, and when they're big the blitting operation (copyPixels) takes too long. While the sounds have already been loaded and are playing, no images are displayed untill copyPixels has finished it's job.

(tl;dr starts here)

So, is there anyway of preloading copyPixels? I could perfectly add an ADDED_TO_STAGE event on the sprite that contains the animtion, pause all sounds, and just play them when it fires. It works, but what will actually happen is the user looking at a preloader at 100% while the event isn't fired yet, I'm sure the majority of them will just think the app crashed, kill it, and try again. It's not "honest" programming, it's hard-coded, deffinetly not what I need. I'm also open to different suggestions.