XP: Addressing STD's and S/O's

pzavecz

I have some friends that I am inviting to my wedding and want to send them a save the date.  I know these people are dating someone but I don't know their S/O's name or I haven't even met them.  They also do not live together.  I was planning to invite them along with their s/o but not sure if I need to put the s/o's names on the STD's.  
I have other friends in relationships and I know their s/o and their names so I was planning to include their name on the STD.  Would it be rude of me to not include the s/o's name for the STD for those I don't know and get that information later when I send out the actual formal invitations?  I have read multiple times that STD's are informal so it's not necessary to include the "and guest" on a STD (which is basically this situation since I don't know the name) and address to the person you know.  But at the same time, shouldn't the person I'm inviting need to know if they get to bring their s/o so they can make travel arrangements for that guest too?  I'm only sending STD's for OOT guests so they can have more time to plan ahead for making travel arrangements.
Advice needed please!

CFM102012

You don't need to put the SO's name on the STD.  You can just send it to your friends since they are the primary invitees. Just make sure to get the SOs' names for when invitations go out.

mpjf1001

ditto to PP
even though I knew most of my guest's name...i only addressed it per household, and if they werent engaged or had been dating for a long period of time I only addressed it to the person I am friends with...
when the invites go out I will add their name or depending on the closeness of my relationship with that person, their significant other, etc I will either write their name or & guest...

music11

Same here.

BMBrinson

ditto! I did put and Guest on some (like my bridal party) just as a way of giving them a heads up that htey can bring someone. If they where engaged or living together, I put them both on there. We just got a save the date addressed to my FI and that had a note that the couple hoped he could come. As couple will soon be family, it rubbed me wrong, so look out for those situations. 

pzavecz

Thanks ladies!  This makes me feel better now...I think I'm going to do what you guys did and just address to the person I'm inviting and leave off the the BF/GF name unless they lived together.  This seems like the simplest and easiest way to do it for STD's.  I don't want to make it more complicated then necessary since these are just STD's.  Then when invites go out, I'll add in the SO's name if they are still together.  Thank you for the help!