rsvp help!

I’m ready to order my invites but my rsvp system is holding me up. I hope someone here can help!

i know I want to include a separate RSVP card that gives instructions to RSVP online without anything for them to mail back.

I was was thinking of putting our website plus a number they could text. But I already have a spreadsheet of invites and Zola + wedding wire wants me to put everything in manually again or use their template. I started but it’s a lot of trouble to transfer

i also don’t have the last names of some guests and how many of them (my FMIL sent them to me and they probably won’t come and I have no way to contact them)

anyway, is there a site that can just be people typing in their own names and numbers of guests? Even if it’s not a specific wedding site but some kind of RSVP site?

or is it weird to put only a phone number on the RSVP card?

or is it best to spring for the postage and do mail in post cards?

help lol!