Visible crew/equipment: When Mrs. MacReady meets the Pevensie children at the train station, the reflector screen is reflected in the lenses of her glasses, as she looks down when she speaks to them. It is also visible when the children first arrive at the house, when Mrs. MacReady says, "There shall be no disturbing of the professor." (00:07:30)
Visible crew/equipment: When Lucy, Peter, and Susan are riding on the ice chunk down the river, when you see a shot of Lucy struggling to maintain her grip on the ice block, immediately after, there is a shot of Peter holding what was supposed to be Lucy. However, it is not Lucy. The person Peter is holding is bigger than Lucy and had blonde-brown hair.
Visible crew/equipment: When Maugrim says "I won't wait forever", crew lights are reflected in Peter's sword. (01:14:50)
Answer: Spoiler alert: this gives some important plot twists away. Sometimes a bit of unresolved mystery improves a story, and I think this is the case here. But the book partly answers your questions. At the end of the last chapter it is shown that Mrs MacReady thinks the wardrobe is just a piece of furniture. She knows nothing about Narnia. But Professor Kirke amazes Peter, Edmund, Susan and Lucy by expressing familiarity with Narnia and explaining that a wardrobe might well be a portal into Narnia. If C S Lewis had not written any more books after completing "The Lion The Witch And The Wardrobe" Professor Kirke's knowledge of Narnia would probably have been an unresolved mystery. But C S Lewis later wrote "The Magician's Nephew" which tells how Professor Kirke visited Narnia as a boy. The final chapter of this book says he took an apple back with him, which he planted in his garden. It grew into a tree, was cut down and made into the wardrobe. So Professor Kirke was not consciously aware of what the wardrobe could do, but with hindsight, he realised that he had set up a chain of events that caused the children to discover Narnia.