Many good questions here:

getting home -- If you can stash a bike ( folding?) for each of you, suddenly 21 miles is an easy 4 hour ride. Otherwise, the usual considerations; walking shoes, map, water. ( or just a plan to stay put till you can get decent transportation.)


communications - 1. getting in touch with your wife. your plan should include land lines, then one of you going to the location of the other. 2. reaching home -- landlines, then computer ( email) then ham gear?

Home prep -- this starts with CLEAR instructions to your au pair. As in " stay in the house unless X" In that case use X to go to X. Here is a list of friends and family.