I wold say cash, have your bank run it through the anti counterfeit machine and put it in a safe deposit box there.
Considering the possibility of a home invasion thing, keeping large amounts of cash in "the house" is not a great idea.
Lots of people/business deal in large amounts of cash much bigger than this. The bank will not be shocked at all.
They won't even ask you where it is from. Frankly, they don't care.