I talked to my FMIL about this last weekend (FILs are hosting) and she said to just do invitations via word of mouth, which is fine with me. I don't plan on sending it out yet, but I was thinking I would just do an email? I know I would want something in writing to refer back to, and that way people won't need to keep asking us. If I do email, it will just go to the wedding party and I was wondering if there is a non-tacky way to let them know that their so's are invited.