Reception Only Invitation

I am having a small ceremony (18 guests) and a larger reception. I purchased an invitation kit to create the reception invitations. For the 18 people invited to the ceremony, I want to include something that states "Please join us at our ceremony at (time and place)." Is this something I hand write on the front (bottom) or back of the actual invitation or do I have to purchase other paper, type it, print it out, and then include it with the invitation and the response card? I really need to get the invites out by this weekend. Thanks for your help!