The joys of multilingual children

While on a recent trip to México, we happened to stay at a hotel with many German, Swiss, French and even Mexican tourists. I have to say it was such a pleasure to see my children being able to make friends with children from all of those countries because of their language skills. One morning they would be splashing in the pool in German and in the afternoon they would be running around using Spanish. I don't believe there has been a single other moment that has more clearly illustrated the value of their multilingual upbringing. I started to think, is there possibly a disadvantage to being bilingual? I have not yet thought of one.