If, when a person is in Narnia, time does not pass in the real world, and children who visit Narnia enter ir one at a time (as in a queue), then after the first child crosses over, how do the other 3 enter in Narnia as well? 

I ask this because after the first child enters, if the time in the real world is stopped, then the other 3 children should not be able to do anything.