Yes, why not? The guy was fine about it. If he truly did not want to go on stage, he could have turned around and left (leaving the pizzas on the floor). What Ellen did was both funny and a lifetime experience for the delivery person that he will treasure for the rest of his life. Not like he's going to lose sleep over delivering pizza to movie stars.
It's a tough question I want to say no, but that would sort of restrict the couple that innocently love each other. How can you enforce this rule without splitting the couple up? What if they accidentally get pregnant -- will they have to have an abortion?
I'm going for no, they shouldn't be allowed to have a child, because I think I would rather to couple be unhappy than sentencing a child to a life of disability.