Are there 'natural laws' on the alignment of dragons? This'd be easier for outsiders, because they ARE alignment, but dragons are living things. Living things on an entirely different set of rules, but still living things. What truly determines their alignment? Is it really just genetic disposition (In which case you need an epic animal handler)? Is it simply the parents (in which case making the dragon good is absolutely no problem)? Or is it divine intervention from the great Dragon Dieties (in which case Bahamut might see fit to turn that green dragon into a metallic equivalent or at least allow it to be good)?

Personally, I think that you should override the rules due to the sheer interesting-ness of the situation of raising an evil dragon into goodness. Have rolls heavily swayed depending on what would happen in a good book, though it could be seen as blasphemy. Hey, that's why I'm not allowed into power seats.

But if you have a burly he-man in the group who prides himself immensely on his masculinity, make the wyrmling disgustingly cute, follow him everywhere, and always squeak 'momma' in obvious reference to him.