It still is a dream. Dicaprio would only be able to see their children if he was in the dream. A phone call from a rich japanese would not be able to change the law enforcement in usa. IF he was in the reality, why did none of actors talk to each other. Remember  it is said that projection feels attacked and look at eachother? I see it this way coz i want to. 
But not see it this way. To think its the reality, the actors played by the children in begnning are different than the ones in the end. Also they are wearing different shoes at the end.  But i think my way is the correct one.