This is about a meetup in January 2024 in Seattle, you could ask the organizer or some of the guests about local advice, and also of course if they are interested
If you want to do it all on your own, well, public library or any friendly community neighbourhood centre might be a good option. Of course coffeeshops and/or restaurants can be a good place too, though sometimes it’s a challenge to have it close to public transport (or parking for you in car-loving US (clichee)) but still not too crowded and with owners patient enough to let you sit for some hours without a megahuge bill.
As for the rest: special designed meetup cards are an option, as are ‘secret-santa’-like games or lotteries. But as guests bring their passion about cards anyway, it’s also enough to provide the frame (in my experience)
Have fun and joy and success, good luck. And for any other questions and experiences, this here is a good place for it.