Not so much topic ideas, just ideas in general.

1, stay away from talking about nostr for the first few meet ups. If its organised here, we're already here.

2, make the first meet literally a meet and greet.

3, after the first few, agree within the group that at every meet 30 minutes is dedicated to one of the members speaking about something they like. Could be stamp collecting or the history of seagulls. It dosent matter.

4, slowly add in more technical adventures, ask people to bring in laptops to use nostr clients, old or second hand phones to learn how to replace the OS with #graphene, set up and fund a paper wallet to give to the host and spread some #orangepill love etc etc

5, like you say, move on to the other stuff. A good way to spread the organising load is to get people to suggest a topic or speaker, everyone votes, the person who suggested it gets to invite them or speak about it.

That's my two pence worth. I see meet ups like this as an opportunity to develop community and mutual aid networks.