They're so cute! And I love the idea of naming them after HP characters. Our guinea pigs were always named after HP characters, too. We had Sirius, Remus, Gilderoy, Hermione, Luna, Rowena and probably one or two more I can't think of right now.
If you say one of them is very curious, I'd name her Luna. Luna is one of the most curious and open-minded HP characters. And the nippy one could be Bellatrix.