One of the things a break back in the UK allowed me to do was to see how much learning a second language has affected the boys ability to speak English. We spent a lot of time with friends who have similar age children and it was interesting for me to compare their linguistic developments.
Luke appears to have been the most affected. Aged 18 months when we arrived he is now 2 1/2. I've never really heard him say much in Bosnian, but understand from his teachers at nursery that it is at a basic level: Yes, no, won't, don't, mine. In other words all the most useful words for a toddler. His English isn't bad at all, but there is a definite difference between him and his peers. Having said that, after 5 weeks in the UK where he only heard English led to the most remarkable advances in his language skills. Who knows whether this jump was due to occur anyway, or whether being back in England encouraged it.
Adam's English is doing just fine. Now 4, he is eloquent and able to communicate really well. His Bosnian is coming along too, although he won't speak with adults just the other kids. He is a long way from being fluent but we think he understands most of what is going on. The only issue that does seem to have arisen with learning another language is that he appears to have developed a stammer when speaking in English. I need to think about the best tactic to take to encourage him not to stutter as I think he is using it for thinking time rather than because he can't not stammer but I do need to do some research on this one (any advice gratefully received!).
We take care to only speak to the kids in English. Partly this is to help clarify for them which language is which. Mainly though it is because our Bosnian is rubbish and we would only teach them how to speak poorly and with a terrible accent. We do lots of reading and have English language DVDs (love CBeebies), but they also have some Bosnian DVDs as well.
The boys are doing so well and I'm incredibly proud of them. They are in a nursery where noone speaks English so they are having to learn Bosnian themselves. I'm pretty confident that if they do fall behind in their linguistic capabilities in English they will rapidly catch up on our return. So, I'm not going to worry about it. If they learn to speak another language whilst they are here then that is amazing, but I'm not going to push them to. After all, if they learn to speak another language whilst they are here then they will be able to communicate with each other without us fully understanding what they are saying. Maybe this isn't such a good plan.