Wedding non-invitation?

So me and my fiancé are taking a non traditional route. Just the two of us and our mums. That been said we would like to send out a card of some sort with a favour. I was wondering If anything knew of a nice poem or wording that can express sweetly that we appreciate them and that it’s not a typical day so we are not having a wedding of some sort but kind of like making a point they’d be the people invited if we were having that kind of wedding. If that makes sense?