Hi, I'm planning to visit Beijing mid of June with my kids.

There is no special preparation for that. It will be a bit hot at that time, and you need to wear T-shirts and shorts. Near these attractions, especially the great wall, you need to prepare some snacks or easy-carrying food in advance, for the food there is in poor quality and rather expensive. Camera, of course, is necessary. Record the memorable scene of your family and amazing view.

Thanks Tina for your advice.