Doesn't matter.
Should they get lost or damaged, unless you have a certified appraisal for insurance purposes, the most - the MOST - you'll maybe get back is the cost of supplies.
The post office considers a quilt something you get at Kmart for $20. They're not in the least interested in your skill or the time you spent creating it.
Sorry, but that's the reality.
Send it USPS Priority w/ DelConf.
That's how I always send my gifts and packages - within the US, and also to Canada and international destinations.
You can send if Signature Confirmation if you want someone to sign for it but it still won't matter if the package is lost.
Same, btw, for UPS and FedEx.
They won't even insure the artwork.
Most of the well-known teachers/quilters - who ship their item all over the place to guilds/shows - have separate insurance policies to cover the items should anything go wrong.