If you have the means to do it, I would.
It's only 16 hours, and you can stop every so often to check on them and check in to horse motels, etc.
Just bring plenty of hay, lug some of your own water with (some horses may be fussy about drinking foreign water) and of course make sure they're in something breakable (flat leather or nylon) for transport.
OP I'm sure if you email the person on the bottom of this page, she'll be able to help you out. https://agriculture.sc.gov/scequineindustry
Finally found the right section..