Nice way to tell guests, No Kids

The only polite thing you can do is address adult guests by name on the envelope. Do not write “The Smith Family”. When someone rsvp’s for their children, that is when you get on the phone immediately and say “sorry we are unable to accommodate anyone who is not listed on the invitation.” Leave it at that. They will tell you if they will be attending or declining at that point.

As Michelle stated make sure you address the invite only to adults invited on the rsvp cards you can have something like we have reserved 2 seats in your honor and then the spots for them to rsvp but I wouldnt put anything about it being a kid free wedding on the actual invite. If you think it's necessary and you have a wedding website you can add something there along the lines of

“We love your children but due to limited numbers this will be an adults only event. Thank you!"

Agree with both above posters. That's the correct etiquette.

I had guests ask me if children were allowed to come to my wedding and I politely told them no and I also put adults only on my invitations. Maybe you can put it on your invitations/on your line invites or website to let them know that children are not allowed.

We put “due to the limited number of seating this is an adults only celebration” on our invitations, I’m still expecting people to ask but will politely tell them no ☺️

Address the invites to only the adults.

Put how many seats you have reserved

Put on your website (should you have one) that it is an adult only affair

On the invitation put "Adult reception to follow"

Do not make it seem like you are doing the parents a favor or asking them to treat it as a date night and "let loose".

On our wedding invites we put “ In order to allow all guests, including parents, a Night of relaxation, we have chosen for a wedding to be an adult only occasion. We can’t wait to celebrate with you”

It's not OK etiquette to refer to who is not invited on the invitation. So, "no kids" and versions of that are considered not good manners.

We have an FAQ section on our website and included a "Can I bring my kids?" portion that says "Unfortunately, we are unable to accommodate children at our ceremony or reception." Once we get our invitations together, we're also planning to address them to "Mr. and Mrs. Smith" and have something like "We have reserved 2 seats in your honor."

We've had a few people say something about their kids being our ring bearer/ flower girl (one even asked when we were buying their kid's tux 🙄), so we just told them informally at that point that we couldn't accommodate children.

I included information cards with our invitations that basically laid out the attire, menu and stated “while we adore children we politely ask that you do not bring them. We want you to enjoy yourself!”
Not one soul had an issue with this request and the majority of our friends and family have children. The only children present (outside of our own) were our 2 nieces and 2 nephews.

We addressed invites to only adults, so far i've only had one group ask if they're 1.5 year old is invited, and i told them "while we love kids, we've opted for a kid free wedding excluding the one child in our bridal party"

This one person (who is FH's cousin we are not close to) tried to guilt me on this but tbh I was with FH when she got married and she did not extend the wedding invite to myself so I'm feeling a little petty.

There's only ONE person I'm willing to make an exception for and that is my FSIL. My nephew will also be 1.5 by the time our wedding rolls around, and she's trying her hardest to secure child care, but her dad was just diagnosed with stage 4 pancreatic cancer and is going to start undergoing treatment soon so if her parents aren't up to taking him all night or siblings are unable to step in I will allow her to bring him. BUT I am very very close with my FSIL and my nephew, we see them on a weekly if not daily basis.

A lot of these are great suggestions.
One I had for my SIL was to put on the RSVP a spot to fill in your “plus one”. That way they know it’s just them and 1 other person. Not their whole family.

I looked up the answer when I was addressing save the dates on a wedding etiquette blog and it said to make sure you address everything to specific people and not "The Doe Family" if you only want the adults to attend. It should NOT be included in the invitation that kids are not invited. If people RSVP including additional members of their family, that is when you reach out and let them know that you are only able to accommodate guests listed on the invitation. The wedding etiquette blog I read said it is quite rude for guests to write in or even ask for additional guests other than the ones listed on the invitation but some people are not aware. It puts the hosts in the awkward position of having to either increase their budget to accommodate or tell their invited guests no which does not feel good.

I am having guests RSVP on here and only added the names of people who are invited. Meaning I did not put any kids names to RSVP for.

But I also put on the invite "We respectfully ask no children attend, thank you!"

Address the save the date and the invite to exactly who is invited. Make it clear that it's an adults-only wedding in the FAQs section of your invite. Bring it up in passing to people who you think this will be an issue with. Let people know early so they can make arrangements.

If someone attempts to RSVP for their kids (BTW, our site on TheKnot only lets people named in the invite to RSVP), let them know you can't accommodate.