As you are all probably aware Ciara and Enya are being raised bilingual. When I was pregnant I ordered a book on raising bilingual children, to be honest I still haven't read it (what can I say my pregnancy wasn't as long as it should have been!), but I think we are doing an okay job so far even without the "professional" advice.
We speak mostly english at home, although I will repeat mself in german if it is very important. If I'm not around Z will speak german with them and when we are out we also usually speak german especially if we are with friends. So far Ciara and Enya have had no problems at the various play groups making themselves understood, but then most adults understand english well enough to get the gist of what is being said. It will be interesting to see what happens in kindergarten where the child/child interaction is more predominant- if the girls then only speak german or if the other kids pick up a few words of english.
Because Z and I mix our languages up when we are speaking to each other (we often swop languages multiple times in a conversation, heck multiple times in the same sentence!) I was very concerned that the girls would also pick up that habit. There are some signs of that, "ich (I) do it" being a prime example but for the most part when the girls are with me they speak english, with a few german words interspersed (because they don't know the english words).
Then every so often I see a demonstration of their awareness that there are 2 seperate languages: Enya was telling me something about her Igel (hedgehog), I understood she was speaking about the Igel, but didn't get the word she was saying before (it sounded like she was swearing!) after the third time I asked her to repeat herself she gave me an exasperated look as if to say "you stupid woman" and said hedgehog clearly. She tried to get me to understand her by repeating herself in the other language which I found amazing!
Z and I have already agreed once the girls are well settled in their kindergarten we will move to both only speaking english with the girls at home, as we don't want them to forget their english. We will still read both english and german books to them at bedtime as well.