lol the pandora is my Christmas present this year.
I was in the same situation as you were, but now I'm not.
I just explained to them that I wouldn't be using this just for gaming, and that I could use it for school work and for programming(its much better IMO than a laptop, due to size). Try to tell them that this isn't just another 'game machine', that might hellp them understand.
I also explained the spec's, my dad is an EE, and he started thinking about getting one for himself lol(once he see's how great mine is he will probably order a few...)
Also just tell them what other people have said, that Craid and ED run their own shops, and are fully certified sellers in their countries, and that there is a whole community behind the device already.
It also might help to tell them that if this does fail, it would teach you a good lesson(parents always love to teach their kids good lessons lol...(no offense to any parents out there, this probably doesn't apply to you if your on these boards)).
If they really want you to set a date set it for end of January.