Sorry this is late as I've not been able to get here before.
A friend of mine lent me a version of the Rosetta Stone for Italian which she had picked up one summer. This form of learning might work for some but it really doesn't work for me at all. I learned more in a class in two weeks (daily classes) than through a daily dose of the Rosetta Stone.
IMHO you would be better off doing a proper German class, at least to start, whether it's online or offline where you have access to a tutor and maybe join or set up a conversation class/group even if it's a casual one. It's one thing to be able to read and write, but another to be able to converse and for this you need a lot of practice, too. You can always ask one of the mums if you can meet up once a week to practice your German whilst the kids play?
Here's a link to some German resources:
http://www.cybergerman.addr.com/