Adult only. Private by design.
What to say on the drive to a lifestyle party

The drive is the last quiet talk. Repeat the plan you already made. If you are not aligned, turn around before you arrive.
The short answer
Say three things before you park: the format of the night, what a no sounds like between you, and how you will leave. Then stop. The driveway is a bad place to invent a new agreement.
Your host invites friends. The host invites friends they'd love to have there. One private link per couple. The drive does not change their list. It only checks that the two of you still mean the reply you sent.
Adult only. Private by design. You confirm you are 18 or older. The host still checks you in. A talk in the car is not a check-in at their door.
Setting boundaries together before a party
Repeat the plan, do not reopen it
Name the format you already accepted. A key party, a play party, and a speed date are three different nights. If you packed for the wrong one, say so now, while you can still tell the host.
Name the time you will leave, and who is driving home. The person driving is the person who is not drinking. That is a plan, not a debate you save for the parking lot.
Name the word you will use if one of you wants a pause. You already chose it. The drive is the reminder, not the workshop.
A no in the car is still a no
If one of you is unsure, say it before the door. You can still go and stay social. You can also turn around. Arriving while you hope the feeling changes is how a no gets rushed inside.
Tell the host if you are out. A cancel from the car is a normal note. Silence until you are in the driveway is the part that strands them.
A private no stays private. You do not owe the host the contents of the talk. You owe them a clear yes or a clear out.
Do not write new rules in the driveway
A new limit, sprung at the curb, is not a plan your partner can use. If something important was never said at home, you are not ready to walk in. Turn around and have that talk where you can actually hear each other.
"Let's see what happens" is not a limit. If you already had one, repeat it. If you did not, do not pretend the car invented one.
A one-sided yes stays hidden even if you talked the whole way. The host does not see a private no. Your partner does, because you said it out loud before you arrived.
Say which night you are walking into
All mutual-yes matches are revealed, whether that happens together, at check-in, or after the short rounds. Say which of those you expect before you unbuckle.
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 that is not the night you want, say so before you are in it.
FAQ
What if we disagree on the drive?
Stop and decide before the door. Stay social, or turn around and tell the host. Do not walk in while you are still split.
Who should drive?
The person who will not be drinking. Decide that before you leave home, and repeat it in the car.
Do we tell the host we almost turned around?
No. If you cancel, tell them you are out. If you come, come with the plan. They do not need the argument.
Is the check-in word the same as a no to another couple?
No. The word is a pause between the two of you. A no to someone else is a separate sentence. Both can be short.
Can we change the format in the car?
You can choose a quieter version of the night you were invited to, such as staying social. You cannot invent a different party for the host.
What if we never made a plan at home?
Then the driveway is too late. Turn around and talk where you can hear each other. A new rule at the curb is not a plan.