My pals from Chicago are coming for five days with their three kids (10-14). They are staying in Union Square. (I am in Oakland, so I'm not up on the latest in SF). They are fairly adventurous and sophisticated eaters. I would be very grateful for recommendations of low to medium-priced places in the city where they won't have to wait two hours for a table and which will fit a group of 6-8 people. I'm particularly interested in places walking distance from Union Square -- say, Tenderloin, SOMA, Union Square, etc.