Thanks. I was frustrated at the lack of a reunion with Ginny at the end of the book, so when I realized that I could write it and have it work with this plot, I jumped at the opportunity.
As far as Lucius and Narcissa - despite their change of heart, they've still committed crimes and are known Death Eaters. Given the fight Shacklebolt gave to arrest Draco, who hasn't committed any confirmed crimes, I think it's fairly safe to say that he wouldn't let those two go easily at all.
And as to your question about Snape, that's a mess-up on my part. Still, they always say that seeing is believing, and the only one who's seen the memories so far is Harry.