Question for parents of bilingual children?

Although I was born in the US, I spoke Greek until I was almost 4. We also continued to speak mostly Greek in our home. So I am fluent in both languages without a hint of an accent in either language. I married a man who isn't Greek. I try my best to speak to my kids in Greek as much as possible, but I do slack off when not around family or Greek speaking people. I tend to say things in both languages. my 5.5 yr old daughter has a very good vocabulary and understands most of it. She chooses to respond in English at the moment. My 2.5 yr old son, also understands and has a decent vocabulary. Just like I label everything in ping while we play, I also say things in Greek. In the car, we play I Spy, but we do it in Greek. Music is another big help. I can sing, write, read and speak fluently in both languages. I read picture books to them when they were tiny, also saying the Greek equivalent of everything in English. I even dream in both. If I get very, very flustered, I might begin to forget an English word here or there and begin to think more in Greek, but that doesn't happen often. As long as my kids keep hearing the words and are involved in the cultural aspects of it, they will grow into it as they get older.