I love the idea of telling them how it is. You have mentioned before that your township has a handful of people. The only thing that stuck out to me is your use of the word "we". I'm assuming it's "we" as in the township government. But, maybe it's "we" as in everyone in the township.

I think given that you have a small township, that maybe using the word "I" along with specific titles, instead of the word "we" might give the letter a more personable feel. I realize that EM is a team effort, but using words like "we" and "township" seem to give a citizen-vs-government feel. Not the "we're all in the same boat" feel. Mention that everyone in the town is a de facto member of your emergency management team, everyone needs to be on the same page and work together. You're only good as your weakest link. Ah, cliches.

Change:
we won't be able to immediately provide the public with drinking water

To:
I won't be able to immediately provide you with drinking water


BTW, I like the idea of putting what you can do at the end.

Are you going to do workshops? I think a collaborative leadership approach may work extremely well in your small community.