1. -You are going to do anything next weekend?
- Yes, my nephews are coming and I am going to show them round London.
- You are taking them to the theatre? (Have you booked seats?)
- No, they’re too young for that. I am going to take them to the zoo.
2. - We are starting early tomorrow. We are going to Ben Nevis.
- You are going to climb Ben Nevis?
- Not me. Tom is climbing it. I am going to sit at the bottom and do some sketching.
Насколько я знаю, going to употребляется при личном намерении что-то сделать, а Present Continuous, когда это намерение запланировано (договорённость с кем-либо или покупка билетов). Насчёт последнего предложения у меня сомнения, так что подумай.