I am co-hosting a sprinkle for my sister. My sister designed the invitations with a photo she made. (I am not really tech savvy and needed help uploading the photo.) She worked on the invitations and had me order them. I kind of wanted to design the wording, and told her I should be the one to take care of this. (She wanted to do it all, and insisted.) I, now, I realize the invitations, don't have an RSVP date or contact information, and they have all ready shipped from the manufacturer. I want to give the guests enough time to decline or accept. Should I include a post-it in there regarding the RSVP information, or write the RSVP info on the back of the photo paper with a marker? Or should I give the guests one week less to RSVP and order new invitations. I am wondering which would be the most proper etiquette to fix this terrible mistake. I am really frustrated, because it looks like I don't care about her shower. How would you fix this sprinkle debacle?