Do you or their father speak another language? If so then speak to htem in your own tongue and they will pick up English along the way. If not then name the things they are learning in the new language first then English and point to the item. Tey to have someone they can talk to in the language they are learning, I was taught greek as an 8 y.o by greek neighbours, I dont know a lot but I can at least be polite and it helped me try to learn other languages, but unfortunately I didnt have anyone else to speak to and my friends moved away when I was 12.

When you teach your children the name of something, or a sentence, say them in both languages and repeat them. Children learn by repetition. I would love to know how you get on, we are getting a Finnish nanny very soon and I have asked that she speak to our children in Finnish and English, (and to me too!). It is a wonderful time to teach them different language, as they are like sponges right now!