We sent out invitations with specific names and no plus-ones for children, but we've already had three couples ask if they can bring their kids anyway. We're renting a smaller venue and really can't accommodate extra people. How do we politely but firmly say no without damaging the relationship?
Have you already set a firm headcount with your venue? If so, that's your honest answer right there - tell them the venue has a strict capacity limit and your final numbers are locked in, so unfortunately you can't add anyone. Keep it warm but brief: "We'd love to have them, but our venue contract is finalized and we're at capacity. We hope you can still celebrate with us!" Most people understand venue constraints better than "we don't want kids," and it removes the negotiation.
The tough part is that three requests means this might keep happening - did you want to shut it down now or see if more people ask first?
I had a friend's wedding a few years back where something similar went down, and honestly the couple just ripped the band-aid off. They called each person individually and said something like "we'd love to have the kids at a future celebration, but our venue has a hard cap on numbers and we've had to make some really difficult choices about who we can fit - we're keeping it adults-only to make it work." Nobody loved hearing it, but nobody got genuinely mad either because it came across as a real constraint, not arbitrary. The key was they sounded apologetic but not wishy-washy about it.
Your best move is probably to respond to each couple the same way soon, before word spreads that some people got told maybe. Keep it about the venue capacity, not about the kids themselves, and offer something small if you can - like inviting them to a post-wedding hangout where kids are welcome, or whatever makes sense for your situation.
Log into answer.
