Hi matt.
I'm from Germany, so here are some answers.
August 1st till31st is holiday time indeed, so some parks can be real crowdy.
Europapark is usually one of the most crowded parks, so try to do it on Saturday/Sunday if possible.
Weekend during Holiday is usual the better time in the parks
If you are looking for a better time, you'll probably have to wait until the kids are back in school - in september.
This could be a great deal, because most of the german parks are open during the weekdays then and its real all-over-the-day ERT-funtime if you are lucky.
Hope i could help , any questions left?
Werner