Would you seriously consider inviting someone that you do not have a telephone number or email address for (or Facebook because they're older)?
I asked my FMIL to PLEASE find out the name of their guests' significant other - she finally said that she could not find out because she doesn't have their email address. Or phone number. Really? How do you communicate with these people???
(So now I am forced to be rude and put "And Guest" on the invite?)