rsvp card and etiquette

I would personally call those guests and say something straight forward like "Hi Aunt Tina, I got your RSVP back and wanted to confirm that you check marked for both you and Uncle John to come to the wedding" and if the mention any adult child, tell them that the invitation was just for her and your uncle.

I would follow up with the guests that have responded to you. If you call or email them, be sure to confirm the names the invitations were addressed to rather than asking them directly who is coming so that you're in control of the conversation; this way they can't list off who they intend to bring rather than who you actually invited.

Follow up with people now and ask who will be coming to the wedding. We had to do that with a few people too.

I think you will have to reach out to all the guest that RSVP'd with a checkmark and not a total number. Let them know at that time you have a certain number of guest allowed and that the invitation is just for the names written on the card. You can also say, "Hello hope your doing well, i'm calling to do a final number for our guest list, you happened to checkmark the card, but I need a total number, will you and (name) be attending?" A nice way to let them know who is invited indirectly.

You could always reach out individually under the guise of checking on numbers and ask that they are aware that it's only them invited. The fact that someone invited their child to the shower with them does indicate that you might have some people assume their kids are invited (even when the invite says otherwise). It's better to clear it early rather than wait until later. If they start getting pushy, stay firm to what you want; it's not their day, it's yours. I always use the budget excuse, because people won't usually offer to pay for their guest.