Obviously, Potter himself. Hermione would probably be there to help with research and problem - solving. Ron might accompany them for support. Dumbledore could be the one who assigns the task of acquiring the artifacts. And there could be some dark wizards as antagonists.
One possible plotline could be Potter exploring ancient tombs to find rare magical artifacts. Another might involve him having to outwit dark wizards who also want the artifacts. And perhaps he discovers a hidden connection between the artifacts and his family's past.
Hermione would likely be there. She is always interested in learning, so she'd be involved in any study related to magical creatures. Ron might also be around, perhaps getting into some comical situations with the creatures. Hagrid is another obvious choice, as he has a deep love and knowledge of magical creatures.
Obviously Percy himself. Also, Annabeth would probably be there as his girlfriend. Grover, his satyr friend, might also make an appearance. And the gods, like Poseidon, Percy's father, would surely play a role, either guiding Percy or testing him on his path to godhood.
Ben himself would definitely be the main character as it's about him being sick. His Grandpa Max is likely to be there, as he is always looking out for Ben. Gwen, his cousin, would also probably be in it, trying to use her magic to help Ben get better or at least understand what's wrong with him.
Well, Naruto is a given. Then there could be other minor gods or spirits in Kami's realm that Naruto meets. Maybe there's a guardian spirit of the ninja world that only appears when someone tries to reach Kami. Also, characters like Kakashi could be involved. He might have some knowledge about Kami that he imparts to Naruto before the journey, or he could even end up joining Naruto on his adventure to Kami.
Obviously, Percy and Annabeth are the main characters. But we could also see some of their demigod friends like Grover. Grover might stop by to check on them and end up getting involved in the babysitting chaos. Maybe Chiron could also make an appearance, giving Percy and Annabeth some advice on how to handle the kids.
Harry is the central figure for sure. Neville Longbottom could play a role. He might be one of the few who know where Harry is hiding and is trying to protect the trunk from being discovered. Hagrid could also be involved. He might bring Harry some food and supplies while he's in the trunk. And there could be some mysterious old wizard or witch who has some connection to the trunk and its magic.
Obviously, Harry Potter himself is the main character. His friends like Hermione and Ron are likely to be there. Hermione might offer her intellectual support and advice on raising the child. Ron could be there for some comical relief and also to provide a male friend's perspective. Harry's godson Teddy Lupin could also be an important character, as he might be someone Harry looks to for inspiration on raising a child without a traditional family setup.
Obviously, Harry, Hermione, and Ron would be the main characters. Hagrid could also be there, being his large and friendly self, perhaps a bit out of place in the glitzy Vegas environment. Dumbledore might make a cameo appearance, guiding them from afar or sending them some mysterious messages. Neville could tag along too, excited to explore a new place.
There could be some antagonists as well. Maybe some dark wizards who were enemies of the Potter family in the past and are still lurking around the house, trying to stop Harry from taking full control. There might also be some Ministry of Magic officials who are interested in the House of Potter for various reasons, such as the possible presence of powerful magic items. And Neville Longbottom could also be involved, as he was a key figure in the fight against Voldemort and could be there to support Harry in this new adventure.