Check out appoLearning.com, because your kids deserve the very best educational apps!
My Yiddishe List
says: My mother's father spoke nothing but Yiddish. He used to communicate with her in pictures because she didn't know enough Yiddish to communicate with him any other way. My ancestry is important to me and it's cool to be able to keep it alive using modern tools!
Yiddish Slang Dictionary
This app is worth the US$1.99. Nothing I could write could be better than the description: "Oy vey, stop your kvetching. You've found the Yiddish Slang Dictionary, to help you shmooze and kibitz. Be warned though, this app contains some words not fit for your bubbe." Not as deep into Yiddish as I would have liked but covered all the basic slang my parents' generation uses.
This US$.99 app has standard conversational exchanges (also known as dialogues :) that you would use when traveling. I have yet to take it into any locale where Yiddish is commonly spoken, but it seems a handy tool nonetheless.
This is the best free general translator out there - with 57 different languages and it always gets it right. Yiddish included.
This is the app you would use to actually learn the language - it has everything you need including quizzes, pronunciations, and interactive games. The only drawback is the price: UK5.99