It is quite easy to create an RSVP form using Google Forms. You can just customize the already provided template and then post the links to your friends and family.
Moreover, you can collect the responses to a Google Sheet. Using [Rapid MailMerge free add-on for Google Sheets] (https://gsmart.in/rapid-mailmerge), now you can email some or all of the attendees quickly from your Google Sheet.
This article will show you how to do all these.