German uses the same Latin alphabet a child already knows from English, with three extra letters to learn: the umlauts ä, ö, and ü, plus the ß (eszett, or sharp s). Because the base letterforms are so familiar, this collection is a gentle way to introduce the idea that other languages tweak the Latin alphabet rather than replace it.
Not sure if German is the right starting point? The guide below covers why tracing should come before free writing even for a familiar-looking script, and how to tell if a Latin-alphabet language like German is a good first foreign script before trying something further from English.