If we're including Mennonites, we need to include the Hasidic Yiddish speakers too.
Mennonites may speak as distinct dialects of German as Yiddish are, but they use standard German as their written language, which is what count in the end.
Of course, Declaring where one language ends and the other begins is itself an artificial construct, a fact which is quite salient regarding German. If Yiddish is a dialect of German, so is Dutch.
