Learning Languages with Duolingo

My Daughter and I are learning Spanish together.  We're using this great website, DuoLingo.com.  The idea is that she and I will be able to talk with our "secret language"

Sounds great, right?  It is.  One minor complicating factor.  My son wants a secret language too.

Yep.  I'm learning German and Spanish simultaneously. 

ich bin ein Pingüino?  Ella es eine Frau?

This can't end well.

(This is not paid shilling.  I really like DuoLingo's approach, and their email reminders prod me to remember my lessons.)