Unfortunately, there is no clubhouse, nor is any planned. The Mueller Neighborhood Association has asked Catellus to consider a space for community meetings in future phases. And there is nothing at Mueller Central.
The Ronald McDonald House has a very nice meeting room that seats approx. 25 people (comfortably) that is available to community and non-profit organizations free of charge. Contact Jan Gunter at
jgunter@rmhc-austin.org for more information. It tends to get booked several weeks in advance - so ask early.
If outdoors is okay, the covered picnic area with grill in Patterson Park (across Airport Blvd.) can be rented from Austin PARD - check their website for details.
Good luck.