Last year we met up at 7 seas, it worked well since its a large space and doesn't require reservations. I would vote for that again. Harmon would require reservations. I'm local to Tacoma so I'm happy to go wherever.
I interviewed at Tacoma last year. Hoping this year goes better! And yes, its a group panel interview, you will be interviewed 3 times in groups of 3. There are 2 interviewers at each panel. Each panel in theory has a theme but all 3 of mine were just get to know you/ask questions about your application. Some people did get asked "what would you do in this situation" type questions. You probably get about 15-20 mins of "air time" per panel. They want to make sure you're not monopolizing the time, that you interact with your panel members etc.