September and October
This is when December Fridays and Saturdays go. If you want a specific date, this is the month to book the activity and the table, in that order.
You do not need final numbers yet. Book for your best guess and adjust; most things, including us, will let you move numbers up to a week or so before.
November
Weekday evenings are still available and are genuinely better: cheaper, quieter and easier for people with children. Send the invite now with the activity named in it. "Christmas meal" gets a shrug; "escape room then dinner" gets replies.
Collect dietary requirements and access needs in the same message so you only ask once.
Early December
Confirm numbers, send the address and the arrival time, and say clearly what people should wear. For us that is whatever they like - you are moving around, occasionally crouching, never running.
The week of
Send one message with the time, the address and what happens first. Tell people to arrive ten to fifteen minutes early. That single message prevents most of the problems on the night.
And if December is already gone, book January. A do in the first fortnight of January is cheaper, easier to get everyone to, and nobody is exhausted.