Well, they might be in complete awe. Poseidon is a powerful god, after all. His presence alone could be intimidating. They could be struck silent or start stuttering out questions about the sea and his powers. Maybe they'd be worried he'd be angry that they're just mortals around his demigod son Percy.
They might be a bit in awe at first. She has a certain presence about her that comes from her being a demigod. Maybe they're curious about her and ask Percy a lot of questions about her later.
Well, in some fanfictions, Annabeth's mortal friends might be initially in awe of Percy. They could be amazed by his powers like controlling water. Maybe they'll be a bit scared at first but then grow to like him as they see how he cares for Annabeth.
In the fanfiction, Percy's mortal friends could find themselves in dangerous situations. Since demigods often attract trouble, the mortals might get caught up in battles against monsters. However, they could also learn a great deal from the demigods, like how to be brave in the face of fear and how to use their wits when in a tight spot. The demigods, in turn, might learn about the simplicity and normalcy of mortal life from Percy's friends.
They would probably be shocked. Demigods have extraordinary abilities, like being able to control water or run super fast. Percy's mortal friends, who are used to a normal world, would be taken aback by such powers.
In fanfiction, when Percy's mortal friends meet Annabeth, there could be a lot of confusion at first. His mortal friends might be in awe of her as she has a strong and confident presence. They may be shocked by her knowledge of Greek mythology which seems so real to her.
In some versions, Poseidon might keep Percy's mother at a distance to protect her from the wrath of the other gods. He could send her gifts secretly to let her know that Percy is okay. For example, he might send a magical seashell that can communicate with Percy.
Grover could be one of Percy's friends to meet Annabeth. He's a satyr and has been with Percy through a lot. When he meets Annabeth, he might be really happy to see another important person in Percy's life.
In many fanfictions, when Annabeth's friends meet Percy, there could be a mix of reactions. Some might be initially cautious, especially if they've heard of Percy's dangerous adventures. But often, they end up being impressed by his skills and his loyalty to Annabeth.