Now that you mensoned it, I havent really thought about it. i read somewhere that it's
Percy Allen Jackson
Annabeth is probably Annabeth (i don't know her dad's name) Chase
Grover (no idea, timothy?! :D, like brandon. t. jackson ;)) Underwood
Ok this is realy hard i give up, i'm sorry, i tried surching in google, but the only thing i found was questions about what their middle names are. I think that only RR knows their middle names.(but probably he hasn't thought about it either.