Why not drive to your local Discount Tire and ask them for 4 used wheel boxes and ship them? That's what I have done both times my wheels have been shipped to Bogart Raving for modifications?
I may end up doing that. I'm also hesitant with a good size dollar amount like this to send them to someone and have them screw me over. I have sold a ton of relatively inexpensive parts on all different forums and eBay but with this dollar amount it's not in my comfort zone.