Adult only. Private by design.
How a host opens the night

Say the format, the end time, and the rooms before anyone has to guess.
The short answer
Open the night in one minute. Name the format, the time it ends, the room that stays dressed, and where phones go. Then stop talking and let people meet.
Your host invites friends. The host invites friends they'd love to have there. One private link per couple. The welcome does not add anyone who was not invited.
Adult only. Private by design. You confirm you are 18 or older. The host still checks you in. A private no stays private.
What to say in that minute
Four facts. This is a key party, a play party, or a speed date. It ends at the time you already put in the invite. This room stays dressed. Phones stay off as cameras. People can follow a list. They cannot follow a toast.
Say whether you are on the list or only hosting. Guests should not have to guess if a hello from you is an invitation. If you are playing, say so. If you are not, say that too.
Do not read house rules they already accepted. Point at the one rule people forget, which is usually the room, the phones, or the end time.
What not to do in front of the room
Do not announce a match. Do not point at a couple and explain them. Do not joke about who said no. A private no stays private. A one-sided yes stays hidden.
Do not send people onto the porch to talk. The porch is not a play room, and it is a poor welcome. Public exposure is still a crime. Keep the opening inside, in the room you said stays dressed.
If someone looks lost, talk to them after, not during the minute. A welcome is not a tour of every guest.
Name the format they actually have
All mutual-yes matches are revealed, whether that happens together, at check-in, or after the short rounds. Say which of those this night is. People packed for the night they were told.
A key party shows one Play Partner at the same time. A play party reveals matches at check-in. A speed date is short rounds, then yes or no. If you changed the format after the invite, say the new one now, and say it was a change.
FAQ
Do guests already know the format?
They should, from the invite. Say it anyway. People forget on the drive, and a new guest may have heard it secondhand.
Do I announce the matches?
No. All mutual-yes matches are revealed by the format, not by a toast. You do not read a list of yeses to the room.
What if I am also playing?
Say so in the minute. Guests should know whether you are on the list. If you are only hosting, say that too.
How long should the welcome be?
About a minute. Format, end time, the dressed room, phones. Then let people talk.
Can I skip the welcome?
Then people invent the rules. Say the four facts. A private no stays private either way, but the rooms should not be a guess.