Maybe there are some small creatures that play important roles too. They could be the friends or foes of the giants. In some stories, these small characters can have a big impact on the giants' lives.
There might also be some human characters. Maybe they are friends or foes of the giants. For example, a brave little girl who befriends a giant and helps him when he is in trouble. Their friendship could be a central part of the story, showing that even though they are different in size and nature, they can still support each other.
There could be some wise old creatures in the book that guide the giants. For instance, an ancient wizard or a talking tree. These characters could add more depth to the stories in the 'Children's Book of Giant Stories' by providing advice or magical elements to the giants' adventures.
I don't know who the main characters are in the 'giant story' because you haven't provided any details about it. It could be a hero who has to face the challenges presented by a giant, or it could be the giant itself as the central figure in the story.
The tiny people themselves can be a group of main characters. Each tiny person could have their own personality, like a brave leader among them, a clever inventor, or a kind - hearted helper. And the giant boy is also a central character. His actions and decisions greatly affect the tiny people. For example, if he decides to move a big rock in his yard, it could either destroy the tiny people's home or open up a new area for them to explore. So he has a lot of power in the story, but also a lot of responsibility towards the tiny people.
I don't know the exact main characters in the 'ghost giant story' since I don't know the specific story. But it could be a brave hero who tries to face the ghost giant, or a group of villagers who are affected by the ghost giant's presence.
The boy is one of the main characters. He befriends the Iron Giant and helps him in many ways.
Since we don't know the exact 'giant man story', it could be just the giant man himself as the main character.
The main character is surely the friendly giant. There might also be some villagers or children who interact with the giant.
Obviously, the giant woman is a main character. There might also be some normal - sized people in the story, like the villagers who interact with her. They could be either friendly or afraid of her.
Often, the main characters are brave explorers. They are curious about the unknown and that's what leads them into the territory of the giant animals. For example, a group of jungle explorers might be the main characters in a story set in a tropical rainforest with giant beasts.