Great idea...just allow at least 45 minutes from end of dinner to start of the show as the Processional is usually packed with just dinner reservation package folks and the line will go back to Japan, again with dinner reservation tag folks ONLY...I would try to sit in the middle somewhere, farther back fine, because the show is definately produced to be seen from straight on. Way to either side makes it hard to see the orator.
Also make SURE you know where to pick up your tags that are good for dinner and the show...in the past it is at the entrance to EPCOT, and you do not want to have to walk all the way back before dinner.
Biergarten is fun, the food is pretty good, expecially the German cold cuts and the sauerkraut and brats...also have a baked fish like salmon, chicken, beef, and good salads...
Their show is fun and like the folks above said, you will sit with others who are usually fun.
Enjoy...Ted