Yes, I'll agree that beer might not be the best thing for the 8-year-old set.
However, there are lots of themes that your DD could choose.
You could start with history, and the role of Germans in the development of the U.S. (The Pennsylvanian Dutch were, by the way, actually Germans.)
You could play around with language, and, together with your daughter, write a paragraph or two that uses (among others) some of the following words: aspirin, automat, dachshund, deli, diesel, Dobermann, fahrenheit, Geiger counter, hamster, kindergarten, Levi´s, nickel, noodle, quartz and waltz. Your daughter could then challenge her classmates to pick out the German words.
Perhaps a talk about history and/or politics might be in order, depending on what types of things you think would not be too high-brow: the Berlin Wall, for example, comes to mind. Engineering? How about cars like the Volkswagen, Audi and Mercedes-Benz?
If that is too serious, then another thing she could do is serve (or at least talk about) typical American food like frankfurters / wieners, hamburgers, pretzels and wienerschnitzels, with perhaps some apple strudle for dessert, and mention that all of those are part of the German gift to American cuisine.
She could talk about famous Germans and their contribution to the world. Examples include composers (Bach, Beethoven, Haydn and Mozart), authors (Goethe) and a number of others (Freud, Goethe, Kant, Luther, Schweizer). She could also focus on Germans who have made it big in Hollywood (Clark Gable, Hedy Lamarr, Peter Lorre, Lauren Bacall, Doris Day, Marlene Dietrich, Douglas Fairbanks, Doris Day - and bringing the list up to date, Leonardo di Caprio and Bruce Willis). Or she could pick a German who has made a strong contribution to the U.S. - ranging from John Astor and Albert Einstein, to Oscar Hammerstein and Henry Kissinger. And if you want something that would be more of a household name to 8-year-olds, how about Dr Seuss?