Do the RSVP and Reception card have to be separate?

Not on the RSVP (they mail that back to you... so they can't keep the info, they may forget to write it down) but I made my invite a design where I included the reception information maybe you can do something like that?

Also we have the same thing with the buffet lunch, so I added a little something cutesy to my RSVP

EDIT TO ADD: I'm also writing in the second blank in the __ of __ will attend/celebrate from afar specifically for each invitee... so if it's a family of 4 I would say __ of 5 blah blah blah so that they can fill in how many are coming.

I guess it depends. Will guests have to mail the RSVP card back or you're doing online/phone/email RSVPs? If so, I don't see a problem with it since they wouldn't need to mail the card back. But if you want guests to mail their RSVPs then yes, separate RSVP card.

No, I will not be asking people to mail back the cards. It would take too long or is impractical.( I live in Barbados and asking those who live here to mail it will be a waste of time and money. And my international guests are far flung including Switzerland, Namibia, Belgium, Haiti, US, UK etc so no guarantee that I would receive their card in time. Doing online rsvp through the website, email, whatsapp,viber and phone.

^^Knowing that now, I think that it's fine to put it on the RSVP cards

Don't put it on the RSVP card, because they won't have it with them on the day of the wedding to know where to go!

You could just have it be an information card that could have your website and RSVP info and the reception, you would just not want to make it exclusively an RSVP card.

Yeah. I like the idea of an information card. Great idea.

Do you think I should put a heading on it?

If the wedding and reception will be at the same place you don't need a reception card. You can just put reception to follow on the invite.

You could make the heading "Additional Information" or something similar since it's not just one thing. Then just add info about the reception, how to RSVP and your wedding website for more details.