He'll bring back a cat of his own :P

After all that dragon talk, I was actually thinking perhaps Charle and Happy were either the dragons reincarnated, or messengers/protectors sent by their respective dragons - but that got ruled out pretty quickly.

I won't be expecting the dragon storyline to be resolved until the very end of the series, but from memory Mystogan found Wendy not long after she separated from Grandine. If he was still "getting used to this world", then it won't be too far fetched to think that maybe the dragons got transported to that world.

edit: Personally I think Gildarts's magic is better translated as Crush Magic. Crash makes sense if he tackles things, but he doesn't try to drive himself into things at all. He touches, and it falls apart.