I don't have any contingency plan, but I think the first thing I'd do is set automatic OoO replies where I assure clients I will look into their requests asap. For longer time periods the best thing to do would try and ask trusted colleagues to take over your work, just as we were discussing in the OoO replies topic here on the forum.
In case you don't get to set OoO replies either... well, imho it's wrong to ask people to be reachable and active no matter what, even in 2017, so I guess they'll have to deal with our absence for a while ?