where his civilizations, including our own

If I make them non-integers, is it going to be possible to insert "leap days" in such a way that the 11-year matchup doesn't get thrown off?

Um, doubtful, but it depends.

You might want to look at what I've got for my Akalet Calendar. Is that a flavor of solution that is acceptable?

maybe just the base characters, with examples of how the combinations work?

Sounds right. I'm not really sure either. Maybe something like http://www.omniglot.com/writing/chinese.htm , more or less.