They would be shocked at first. Minato would be filled with pride and joy seeing his son all grown up. Kakashi would respect Naruto's strength. Obito might be a bit envious of Naruto's popularity but also admire his spirit. Rin would be very friendly towards Naruto.
When Team Minato meets Hokage Naruto in a fanfiction, their reactions would depend on their individual personalities. Minato would be overjoyed and would immediately start asking Naruto about his achievements and how he has led the village. Kakashi would be his usual calm self but would show his admiration through his words and actions. Obito, who has had a difficult journey, might initially be hesitant but then would be inspired by Naruto. Rin would be the most excited, perhaps jumping up and down and saying how wonderful it is that Naruto is the Hokage. This encounter could also lead to a deeper understanding between them all and a strengthening of the bonds between generations.
Minato would react with concern and a sense of responsibility. He'd try to figure out the root of the problem. Kakashi would be reserved but still show empathy. Obito would be more upfront and vocal about his desire to help. Rin would be very gentle and motherly. For example, Minato might ask the reader about her family or dreams that have been shattered. Kakashi could share his thoughts on how he coped when he felt lost. Obito might offer to take the reader on adventures to show her the good in the world, and Rin would make sure she has something to eat and a place to rest.
They would be empathetic. Minato, as Naruto's father, would especially feel a deep sense of pain seeing his son struggle. He would want to reach out and comfort Naruto during his lonely times when the village shunned him because of the Nine - Tails.
Naruto would be devastated. He might blame himself for not being able to protect his son. Sasuke would be angry and would likely go on a hunt for the perpetrator. His friends like Sarada and Mitsuki would be heartbroken. Sarada might vow to become stronger to prevent such a tragedy from happening again.
Minato would likely be extremely shocked. Naruto is his son, and the idea of Naruto attacking him would be completely unexpected. He would probably try to talk to Naruto first, to find out what is wrong and why he is being attacked.
Boruto's reaction would be complex. He'd be heartbroken, for sure. He might start to question his own worth and purpose. But over time, he'd realize that he has to carry on Naruto's legacy. He'd become more serious and focused. He'd also become more empathetic towards others, understanding the weight of sacrifice. He might even start to study Naruto's techniques and leadership style more closely, trying to emulate the things that made Naruto such a great Hokage and hero.
One possible plot could be a training session. Team 7, consisting of Naruto, Sasuke, Sakura and Kakashi, might meet Team Minato, which includes Minato, Obito, Rin and Kakashi in his younger days. They could engage in friendly sparring matches. Naruto would be excited to meet his father Minato and learn some new jutsu from him. The two teams could also exchange stories about their adventures, like Team 7 talking about their battles against the Akatsuki, and Team Minato sharing their experiences during the Third Great Ninja War.
In this fanfiction, there could be an epic battle of skills. Team Minato, with their unique abilities from their time, could test the mettle of Team 7. Maybe Minato's lightning - fast speed would be pitted against Naruto's new - found powers. It would be a clash of different generations of shinobi.