Quote: from MushroomSatsujin at 2:11 am on Sep. 16, 2008
Tell them. it aint like you robbed a store, its just a stupid speeding ticket. 
I assume with the emphasis the OP put on not telling their parents, that the consequence isn't as easy as the comprehension of it just being a simple speeding ticket. So telling them and acting like it's no big deal, when it really shouldn't be, might not be the best thing.
But it might be the only thing you're in for. Or else hope your aunt can talk your grandmother out of ratting you out. Depending how "severe" this consequence might be all depends on the advice that can be given. So, JordanShadows, you'll have to be more specific with that for better advice.