Difference of words

There are words that, while they are English, are not used very often in everyday speech in the U.S. We have found that after two years in a British school, our English (especially the girls) has changed to include the following words: lovely, quite, keen, sweetie, trousers, rubbish, proper. Some examples: "It is a proper croissant", "This is quite lovely mommy isn't it?", "I quite like it.", "She is really keen to play outside." , "Mommy, can I have a sweetie?", "I got my trousers wet today." Some of these words Jason and I have accepted with ease but ones such as "trouser" are a little bit harder to accept. In the end I have to smile whenever I hear Ali say trousers b/c it just sounds so strange to me. It is just part of living in another culture that is interesting.