What if you have to take a child to daycare? Here is one person's solution. This is a "Burley d'Lite" two child trailer. They aren't cheap! But I owned one just like this and it was one of the best investments I ever made! I loved using it. The wheels pop off and it folds down flat in seconds. You can store it or put it in the trunk of a small car. After I finished with mine I sold it to a friend.
Note the way this bike is locked. Front wheel, frame and rear wheel and trailer. You must lock them all r you will loose them. I hear bike theft is even worse in Europe.