slim23,
Almost 30 years agp, my Grandad gave me a horse, brought it out to Colorado from Illinois. We lived at 7000 feet then. It took her a good month before that mare aclimated to the altitude. Could not ride her for the firstweek she was so tired from just walking around.
I would counsel you to leave yours at home and rent horses here. I don't see how they will make the 1200 mile trip, then be any good to you at 10,000-11,000 feet. Might even hurt them. Conditioning is great, my horse was in good shape too, but going from 600 feet to 10,000+, trying to pack you around/or an elk out is not going to happen given the experience I've had. I know there are outfits that rent here in Colorado for $300-400/wk. Figure that against the savings of pulling a trailer.
Even when we took our horses hunting back then, they lived at 7000 ft and we took them to 10,000+, they would blow a little extra the first day or two.
Might also call a vet out here and ask his opinion. PM me if you want, I'll get you the name & number of some local vets.