Where's a good place to get friends together a Saturday 3 - 6 pm?

We're coming back to Brussels where we lived from 2003 - 2007 and want to invite old friends to meet up with us informally not over a sit-down meal. We've got two kids age 7 and 14, some of our friends also have kids, some don't.

Can you recommend some places near Auderghem, Watermael-Boitsfort,or Ixelles?

Thanks a lot!