Well, I'm not going to email you since that's what the forum is for.
A few suggestions...
Be sure to plan the frequency that you use between 28.3 to 28.5 MHz SSB. That way even Tech class operators can join in, since that Tech class operators only have those voice privileges on 10 Meters. Your post said "simplex" which makes me think you want to use FM, but the FM portion of the band is only allowed for General and above classes. (Other than 10 Meter repeaters, everything on HF is simplex.)
Also, SSB will work a lot better than FM for weak signal work, which is what one would expect if the power grid is offline and you're huddled up in a cave hiding from zombies, aliens, tornadoes, or whatever else might have taken down the grid.
Power: 5 Watts could do it, but probably not very well. A lot depends on the antenna and terrain of the area. Most HF radios can do 100 Watts on HF, so power shouldn't be too much of a concern. Just use the amount of power necessary to maintain contact.
Time of day: 10 Meters works best during the daylight hours, but for short range ground wave propagation about any time should work. 10 Meters is a hard band to predict. If conditions are good then a simple antenna and modest power will work just fine. When band conditions are bad you may have issues with a beam antenna running 1000 Watts.
As far as coordinating this with other amateur operators in the area, I'd suggest starting a Facebook page or group. There you can put all the info, get others to join in on the discussion, and set up your plans. Maybe set up a weekly net on a frequency that's not in use to get participation started.
One other bit of advice, don't sweat the small stuff. While there's always a possibility of the collapse of civilization, let's be honest, it's probably not going to happen. And if it does, it's doubtful that many people are going to be on their ham radios. They will be seeking cover from the zombies.
You can also "rehearse" contacts by just getting on the air. Call CQ, talk to people, enjoy the hobby.
I wish you luck.
