We used to travel a lot and all over the world (before the baby

) and always just let our clients know when we would be out of office and if we would be available at all while we were traveling. I will admit that we
always book hotels with WIFI and/or find an internet cafe at least once a day to check in on things, but we have sites like this to maintain as well as servers so can't really ever be 100% offline for long periods of time.
If we ever did need to be totally unavailable for some reason I would sub out what I could and hire someone qualified to handle the more technical things that we do on a weekly basis to just check in on the things I needed to check on (client sites, servers, etc.) in case of emergency.