Harry might encounter some magical nomads. These are wizards and witches who don't settle in one place but travel around the wizarding world. They could introduce Harry to different cultures within the wizarding community and show him some unique magic that he has never seen before.
Well, perhaps Harry would go to a wizarding beach where he could practice magic without the usual Hogwarts restrictions. He might meet some new magical creatures that are only found near the sea.
One common theme is discovery. Harry and his friends often discover new places in the wizarding world during their vacations. Another theme is friendship. Their relationships are strengthened as they go through different adventures together. And there's also the theme of magic outside of Hogwarts. We get to see different types of magic being used in various vacation settings.
Well, it could be about Harry and his friends discovering a magical place where time stands still and they can have an eternal vacation. They might encounter new magical creatures and learn spells that are only available in that special place.
I'm not sure specifically as I haven't read this particular fanfiction. But generally, in a Harry Potter fanfic, a 'forced vacation' could be about a character being made to take a break from their normal wizarding life. Maybe Harry is forced to go on a vacation away from Hogwarts due to some plot device like security reasons or a magical decree.
In many Harry Potter summer vacation fanfictions, Sirius Black is also a character that shows up. Given his relationship with Harry and his status as a wrongly - accused wizard. He could be involved in protecting Harry during the summer or helping him with some secrets about his family. Luna Lovegood might also be included, with her unique perspective on magic and the wizarding world, she could add an interesting element to the summer vacation stories.
Well, perhaps Harry and his friends could visit the famous Vegas shows. They might be amazed by the magic tricks there, thinking they're similar to the spells they know. And they could explore the glittering casinos, but of course, not for gambling in a proper 'Harry Potter' way. Maybe Hermione would be interested in the libraries in Vegas, if there are any special ones.
It could be about how the community in the Harry Potter world comes together to face challenges. Maybe it shows how different characters from the series, like students at Hogwarts, professors, and even magical creatures, work as a group to achieve a common goal, such as fighting against the Dark Arts or protecting the wizarding world.
One great 'Harry Potter Takes Control' fanfiction is 'The Power Within Harry' which shows Harry taking control of his destiny in a unique way. It has him making decisions that are different from the original story, like taking charge of his magical training earlier.
Well, it could be about Harry Potter having a kind heart and taking in various 'strays' in the wizarding world. Maybe he takes in lonely or lost magical creatures, or perhaps other students who don't really have a place to belong. It might explore his nurturing side and how these 'strays' change his life or the Hogwarts environment.