Why did Mum agree to go for dinner?

M: Mum, what will we have for dinner?
W: Maybe fish, chicken soup and what do you want to eat?
M: Mum, why don’t we eat out for a change?
W: Oh, that’s a good idea. Actually I’m very tired today.
M: Mm, let’s go to KFC this time.
W: Ok, then, you’ll drive, won’t you?
M: Ok, ok. Ah, here we are. Mum, what would you like to have? I’d like a hamburger.
W: I want one, too. And some desserts and beverages?
M: Yeah, a glass of Pepsi, an ice-cream cone and an apple pie.
W: Ok, you go and find the seats.