It's fine, I'm still shooting Kodachrome 25 at 25, and that's been expired for 10 years.
Shoot it at 64, and get it to Dwayne's as soon as you're done.
As for the 30th vs the 31st, I'd get it there before the 30th to be safe, but originally I think they said December 10th, then it was the 30th, and there was at least one interview where the 31st/end of year was mentioned. To be safe assume it's still noon on the 30th.
Just sent them another 5 rolls, got 6 left, heading to the Grand Canyon soon. Have forms pre-typed, as well as USPS priority small flat rate boxes all ready to go.