Harry would see it as an opportunity for Sirius to finally have a normal life. He would support Sirius wholeheartedly. He might even ask Sirius to write down his adventures so that he can read about them, knowing that Sirius is out there living his life to the fullest after all the hardships they've been through.
Sirius would probably be overjoyed at first. Harry is his godson and he cares deeply for him.
Sirius would probably be very worried and immediately try to help Harry. He might use some basic healing spells he knows.
One possibility is that Sirius, having finally been vindicated and after the chaos of the war, decides to travel the wizarding world to heal. He might visit old friends and places from his youth that he couldn't before due to his false imprisonment. He could be on a journey of self - discovery, trying to find his place in a world that has changed so much.
He might be extremely hurt and confused. Harry has always seen Sirius as a sort of father figure, so being disowned would be like a huge blow to his emotional stability. He could become withdrawn and start to question his own self - worth.
Sirius might react with a mix of surprise and protectiveness. He would be like an older brother or father figure. He'd make sure they were safe and not doing anything too risky.
Ginny might be extremely embarrassed. She would probably blush deeply and try to hide behind Harry at first.
Harry may also feel a sense of adventure. Despite the situation, he's used to facing strange and dangerous things. He might start to think about how he can use this situation to his advantage, like finding out more about his parents or the secrets of the wizarding world that Sirius might know. He could be a bit excited as well as scared. For example, he might be thinking that this could be a chance to get away from the Dursleys for good.
Sirius would have a big impact on Harry's understanding of family. Harry has always longed for a real family, and Sirius would show him what a loving and supportive family can be like. This would make Harry more open - hearted and less guarded. He would also be more likely to forgive those who have wronged him in the past, as Sirius might teach him the value of forgiveness. Moreover, Sirius' love for adventure could make Harry more adventurous in his exploration of magic and the wizarding world.
At first, Harry might be confused. He's used to Ginny being there for him, and suddenly she's ignoring him. He might try to reach out to her a few times, but when she doesn't respond, he could become a bit withdrawn himself, thinking that he's done something wrong.
At first, Harry might be extremely confused. He trusts Sirius to a certain extent, but being kidnapped is still a shock. He would probably ask Sirius a lot of questions like 'Why are you doing this?' and 'Where are we going?'