We do a similar thing to the OP on both mine and my wife's iphones using Google Calendar (set up via exchange). We both have separate calendars, but both our phones are set up to display both calendars. That way we always know where each other are going to be with work at any stage in the future.
Its particularly useful when my wife adds something to her calendar and I get a text notification from google to highlight it to me, just in case I miss it.