I occasionally hunt ol Union lake and can confirm that it can be very popular. It's a pretty good place to find a few early resident geese but it slows down quickly as the pressure increases. Fisherman are usually present and sometimes indifferent of fishing right in your spread. If you get upset easily, this is not the place for you.
As for the maurice....there were plenty of ducks there a few weeks ago but it was colder than and rather stormy when I was there.