Grover could be a main character too. His ability to sense danger and his connection to nature could be important. For example, he could use his powers to find a safe place near the crash site or to communicate with nature spirits to get help for Percy and Annabeth after the car crash.
Annabeth Chase could also be a main character. She might be the one who comes up with a plan to get out of the situation after the car crash. Her wisdom and strategic thinking would be very useful in dealing with any threats that emerge because of the accident.
Obviously, Percy Jackson himself would be a main character. He could be the one driving the car or trying to protect his friends during the crash. His powers over water could play a crucial role in the story.
One idea could be that Percy, Annabeth, and Grover are in a car on their way to a new demigod camp when they get into a crash. Percy uses his water powers to protect them from the worst of it. Maybe the crash was caused by a monster in disguise that was trying to stop them from reaching the camp.
For sure Percy. A merman who is an outcast among his own kind because he has a unique ability that others are jealous of. And Nico di Angelo could be another main character. Nico's connection to the underworld might play an interesting role when dealing with the merman's world which is so different from the underworld but still has some similarities in terms of being a hidden and often misunderstood realm.
Obviously, Artemis. She is in charge of the Hunt, and her relationship with Percy would be central to the story. Then there could be Zoe Nightshade. She was a very important member of the Hunt in the original Percy Jackson lore. If Percy is adopted by the Hunt, she would have a big influence on him, either as a mentor or as someone who initially opposes his presence. And the wolf is also crucial. It could be a mysterious figure, maybe a messenger of the Hunt or a guardian of some sort, and it would be involved in Percy's journey every step of the way.
Maybe the child of one of Percy's friends from Camp Half - Blood could also be a main character. For instance, the son or daughter of Grover. They could have unique abilities related to nature and prophecy, and bring a different perspective to the story compared to Percy's kids.
The main character is Percy Jackson. Other characters could include Tyson, Percy's cyclops half - brother. Tyson could come to the school and help Percy with any underwater - related issues, like if there was a problem with the school's plumbing that was actually caused by a water - based monster. And there could be a group of students who form a sort of 'Percy Jackson fan club' within the school, always eager to hear his next adventure story.
Annabeth Chase could also be a main character. Her wisdom and knowledge of architecture and mythology would help in understanding the Horsemen's motives and weaknesses. She could be the one to come up with plans to stop them, like finding ancient artifacts that could be used against the Horsemen.
Obviously, the baby gods themselves could be main characters. Each with their own unique personalities and powers. For example, a baby god of the sea might be curious and mischievous like Poseidon. Another could be a demigod who discovers the baby gods and takes on the role of their protector. This demigod would have to deal with the challenges of protecting these powerful but inexperienced beings. And there could also be an older god who has an interest in the baby gods, either for good or bad reasons, and becomes a central figure in the story.
The main characters would surely include Percy. Then, there could be Tyson, Percy's half - brother. Tyson could be really worried about Percy and use his strength to protect him while he's sick. Also, Chiron in his disguised form as a teacher at the school could play a major role. He has a lot of knowledge about demigod illnesses and could guide Percy's friends on how to help him.
Definitely the children of Percy and Annabeth. Their kid would inherit some of their parents' skills and personality traits. Maybe they'd be a great strategist like Annabeth and have Percy's water - related powers. Another main character could be the son or daughter of Nico di Angelo. They'd likely have some spooky underworld - related powers and a brooding personality.
Obviously Percy himself would be the main character. But there could also be sea nymphs like Amphitrite who could play a big role in raising him. Maybe Triton, son of Poseidon, could be a mentor figure to Percy.