There are two ways to show the Pevensies being brought into Narnia. From an outside view as Copperfox mentioned, and from their own view as the General suggested. I would want the latter. It would look much better seeing their world fade away, and then be replaced by Narnia.
When I think of them exiting this world, I think of it happening like it describes in MN when Polly disappears: "immediately, without a flash or a noise or a warning of any sort, there was no Polly." That, of course, being the outside view of seeing them disappear. For them, there was a warning.
As for the scenes I am eagerly anticipating, Lucy's meeting with Aslan at night is one. I also would love to see when Aslan plays with Trumpkin, but just like in LWW when they took out the playful romp with Susan and Lucy after Aslan came back to life, I doubt they will put that in.
MrBob