Several studies suggest that 60% of all cattle dairies Nation-Wide have at least 10% of their herd infected with Johne's. Studies also say that most cow dairymen are not even aware of the disease. If you are thinking that by using cow milk you will avoid exposing your kids to CAE then you should read more on these studies.
While trying to avoid CAE you may be inadvertently exposing your kids to Johne's which is just as devasting.
For more articles about Johne's
http://www.johnes.org/handouts/index.shtml#general_articles