Doing nothing else is the simplest thing that might work.

You have implemented the big idea and had success attracting users and are still attracting them.

The hard problem is local community building. It is not adding generic features that are available from iOS, Android, and HTTP.

Actual meetups is the meaningful metric. Achieving market liquidity (people who want to meetup can find a meetup, people who hold a meetup have people show up).

Ultimately, communication should happen around the site person to person, not through it. It should be between people not bottlenecked.

If there is a lesson from HN, it is the 90% of iceberg below the surface is what matters most. Good luck.