You could put it as a calendar entry and use google calendar sync to share it between devices

You can sync/share multiple calendars, so you could if you wanted set up a google calendar specifically for sharing items without affecting your own real individual device calendars, and either of you can of course edit it online as well then too.

Obviously this wont be a word document, but its a way of getting what you seek

http://www.google.com/mobile/sync/
Plenty of tutorials on getting this to work if you google it