In The BFG, what happens after Sophie tells the BFG she saw him blowing the trumpet?

At the very beginning of The BFG, Sophie sees the BFG walking down her street carrying a suitcase and a long trumpet. He is looking into the second-storey windows of the houses on the opposite side of the street, and he stops at the house of the Goocheys. He takes a glass jar from his suitcase, and

He unscrewed the top of the jar and poured what was in it into the end of...

At the very beginning of The BFG, Sophie sees the BFG walking down her street carrying a suitcase and a long trumpet. He is looking into the second-storey windows of the houses on the opposite side of the street, and he stops at the house of the Goocheys. He takes a glass jar from his suitcase, and

He unscrewed the top of the jar and poured what was in it into the end of the long trumpet thing. Sophie watched, trembling.She saw the Giant straighten up again and she saw him poke the trumpet in through the open upstairs window of the room where the Goochey children were sleeping. She saw the Giant take a deep breath and whoof, he blew through the trumpet. No noise came out, but it was obvious to Sophie that whatever had been in the jar had now been blown through the trumpet into the Goochey children's bedroom. What could it be?

Later, when Sophie is with the BFG in his cave, she tells him that she saw him blowing the trumpet and asks what he was doing.

'If you is really wanting to know what I am doing in your village,' the BFG said, 'I is blowing a dream into the bedroom of those children.'

'Blowing a dream?' Sophie said. 'What do you mean?'

'I is a dream-blowing giant,' the BFG said. 'When all the other giants is galloping off every what way and which to swollop human beans, I is scuddling away to other places to blow dreams into the bedrooms of sleeping children. Nice dreams. Lovely golden dreams. Dreams that is giving the dreamers a happy time.'

He tells her that he keeps dreams in his jars (he has a huge collection on shelves in his cave), and uses his trumpet to blow them into the heads of children who are sleeping at night. Sophie is intrigued by this idea, and the next day the BFG takes her to dream country, where he uses his huge ears to locate the invisible dreams and then catches them with a net at the end of a long pole. He catches one very nice dream and one very bad nightmare, and when they get back to giant country he blows the nightmare into the head of another giant.