Went to a Brewers game vs. the Atlanta Braves, a team we had never seen before in Milwaukee. It was a weekend game, so the ballpark was almost full if not at capacity. We usually either buy our tickets from a scalper or buy at the main box office at the main entrance.
We got stuck in 409, row 20 which is high up there. Not the best seats but still good enough to enjoy a Major League Baseball game. The first base side definitely gives fans a better look at the jumbo tron and the outfield area so at least section 409 had that going for it.
The sausage race is fun to watch from so high but your kids will most likely enjoy seeing it up close. They serve five different types of sausages at Miller Park; Italian, hot dog, Brats, Polish and Chorizos.
"Brat Boys" is the concession stand that will carry them all, they are scattered all over the ballpark, you will see one on the way to your seats.

P.S. - If you're sitting in the 400s, you will want to take the escalator up to your seats. It serviced all levels and you can find them at the right, left and homeplate gates. Depending on where your seats are, you'll have to determine which escalator will be the closest to your seats.