You don't say which lenses you're using on the 1D but I guess they're pretty big, so you're not going tomgain a great deal by travelling with large lenses on a smaller body.
However you say that photography is an important part of your excursions, and you're a 1Dx user so I guess you really want something that is as close to the 1Dx but much smaller - the 6D. I apologise now to all those who have just raised an eyebrow at me mentioning '6D close to 1Dx' in the same sentence.
With the 6D you'd need small lenses to capitalise on it's size: the 24-70 IS is a very good match for the camera; lenses like the cheap 40 pancake are excellent enough to satisfy any 1Dx user.
The other small FF alternative that's compatable with EF lenses is the Sony a7r.
If you didn't want to purchase smaller, lighter Canon lenses, assuming you haven't already got any suitable, and were prepared to go for a camera with a smaller sensor then there are a miriad of options.
I guess I'm thinking that for anyone used to handling a 1 series the 6D + lightweight lens is gonna seem tiny.
X100s. Full feature set, great IQ, compact, no extras needed on the go other than a couple batteries.