After reading your post, I can't get past the imagined looked on my wife's face if I asked "Can I bring my orchids on vacation with us"

I don't live as far upstate as you're going, but I keep most of my plants(paphs, phals & oncidium intergenerics) outside and they seem to love it. The rain is on the acid side(5.7-6.0), not sure how vanda's would react to that. It will also get down to the 30's in mid to late Sept at night.
Hope the 'chids enjoy the vacation.
Bill