Will it be weird to send an invitation if someone has already RSVP'd?

Send them invitations even if they RSVP already. STD is not a formal invite.

Send them a formal invitation. It's an etiquette thing.

I agree with the others. A formal invitation is required.

Send a formal invite. RSVPs may change or they may not. Either way to have a small card with dates times and location on it for the day of would be helpful

I too have an option on the website to rsvp, but I also plan on sending a paper invite.

Yes, send the invitation.

I've already had 4 RSVPs based on our STDs and I don't plan to send invites til August. Send the invites anyway.

Still send the invite. I also had people RSVP after I sent STDs but I sent invites to everyone.

Ok cool will do! Thank you ladies!

I'd still send the invite for etiquette purposes. If someone received a STD, they are expecting an invitation. Not receiving one when they know they are supposed to could cause them to question whether they're still invited (extreme situation, I know, but I'd assume I'd been uninvited if I didn't receive an actual invitation after my STD).

Also, sometimes plans change. Receiving the invite will serve as a great reminder to people who have already said they'd be there to double check that all their plans are set or let you know if their situation has changed.

Personally, if we end up setting up an online RSVP form, I would keep it disabled until the day I stick the invitations in the mail so that people don't RSVP super early and them have to change their minds because something came up.

You could attach a little note that says "Thank you for already RSVPing! We can't wait to have you there for our special day."

I may run into this as I plan to provide the website too. I hope if they get an invite that they dont get confused after they RSVP online before the invitations.