Adventure is likely a theme. The father's encounter with the dragon probably leads to all sorts of exciting and dangerous situations that they have to overcome together. It could also be about discovery. Maybe the father discovers a whole new world or a new side of himself through his relationship with the dragon.
One possible theme could be friendship. The father and the dragon might become friends despite their differences, showing that friendship can cross boundaries.
Another theme could be courage. Facing a dragon is no easy feat, and the father must show courage throughout the story. And perhaps there's a theme of family too. The fact that it's a 'father's' dragon and it's a bedtime story might imply that the father is sharing his experience as a way to connect with his family or pass on some values.
Since I'm not familiar with the specific 'my father's dragon bedtime story', it could be that the dragon in the story has some special powers. For example, it can fly really high and show the father a whole new world from above. And the father might learn some important lessons from the dragon, such as the value of courage and friendship. The story could end with the father sharing his amazing experiences with his family at bedtime.
Friendship is also a likely theme. Maybe Jace meets different characters in his story and forms strong bonds with them. For example, he could befriend a lost fairy or a talking mouse. Through these friendships, Jace learns about kindness and cooperation.
One possible theme could be friendship. Maybe Rosie has a best friend in the story, and they share secrets or have little adventures together at bedtime.
One possible theme could be family heritage. The garden could be a symbol of the family's history and values passed down from the father. Another theme might be the connection between nature and family. Just as the father takes care of the garden, it can represent how he nurtures the family. Also, the garden could be a place of memories, so memory and nostalgia could be themes as well.
One possible theme could be sacrifice. The father might have to sacrifice his own time, career, or personal desires for the sake of his family or children.
Another theme might be growth and development. Through the father's help, the characters in the story, whether it's his children or other family members, might experience personal growth. For instance, they could learn new skills or gain more confidence.
One possible theme could be love, as it might be about the love between Bianca and her mommy.
A third possible theme could be discovery. The Scotsman may discover new things about himself, other people, or the world around him during the train ride. He could meet people from different backgrounds on the train, and through conversations with them, gain new perspectives. The changing landscapes outside the train window could also be a form of discovery, as he sees parts of Scotland he may not have known before, and this could lead to a greater appreciation for his homeland.
There could be a theme of discovery. The traveler discovers new places and cultures, and the wife might also discover new things about herself during his absence. Additionally, the theme of loyalty is likely, as the wife stays faithful and waits for her husband, and the traveler remains committed to his wife while away.
Love could be a major theme. The love between the traveler and his wife despite the distance. Also, longing. The wife longing for her husband's presence when he's away traveling.