A plot could revolve around a prophecy that says only baby Team 7 can save the village from a great evil. Kakashi is tasked with training them from a very young age. He has to adapt his teaching methods to their baby capabilities, like using simple toys to teach them about chakra control. He also has to keep them safe from those who might want to stop the prophecy from coming true.
Maybe in the fanfiction, an enemy uses a jutsu to turn Team 7 into babies. Kakashi then has to figure out how to reverse the jutsu while dealing with the cute but sometimes troublesome baby versions of his students. For example, Naruto might be constantly hungry and crying for ramen, Sasuke could be moody and brooding even as a baby, and Sakura might be overly energetic and trying to 'help' Kakashi in her own clumsy way.
One plot idea could be Minato discovers Kakashi's hidden potential as a baby. Maybe he has a special chakra signature that Minato realizes can be harnessed for great things in the future. Another could be Minato taking on a father - like role to baby Kakashi, teaching him basic ninja skills early on.
A possible plot is that Sakumo discovers Kakashi has an extraordinary talent very early on. So he tries to find the best way to nurture it without pushing the baby too hard. For example, he might give Kakashi a small kunai to play with and notice that he has an unusual grip and focus on it. Then, he could start introducing very basic ninja concepts related to the kunai, like balance and aim. Or perhaps there is a story where Sakumo has to leave baby Kakashi with a friend for a short time and when he comes back, Kakashi has learned something new and unexpected from that person.
Maybe they time travel to a point where a major battle was lost in the past. Kakashi and Team 7 could change the outcome of that battle. For example, if they go back to the battle against the Nine - Tailed Fox when it first attacked Konoha. They might be able to prevent some of the destruction and save more lives. Or they could travel to a time when a powerful ninja was wrongly exiled, and they work to clear that ninja's name and change the course of history.
One idea could be exploring Kakashi's relationships within the Anbu. For example, his friendships or rivalries with other members. Maybe there was a particular mission where he had to rely on a teammate he didn't trust at first.
One interesting story could be about Kakashi taking Team 7 on a special mission that involves time travel. They end up in the past and have to interact with their own predecessors. It's full of action and character development as they see how things used to be.
A possible plot is that Naruto discovers a hidden power within Kakashi that even Kakashi was unaware of. This discovery leads them on a journey to explore the origin of this power. Maybe it's related to an ancient clan. As they dig deeper, their relationship grows stronger and they face many challenges together from enemies who also want this power.
One idea could be a story where young Kakashi has to protect a young Naruto from a group of rogue ninjas. It could show Kakashi's early skills and Naruto's innocent yet determined nature.
One idea could be Sakura exploring her unique family dynamic with Kakashi as her father. Maybe she inherits his ninja skills in an unexpected way.
Well, perhaps the child in the 'kakashi and sakura child fanfiction' gets involved in a mysterious mission that only they can solve because of their special heritage. The child could be the key to uniting two feuding ninja clans, using the influence of Kakashi and Sakura in the ninja world. Also, the story could focus on the child's relationship with their peers, who may be in awe or jealous of their powerful parents.
A really interesting plot for 'kakashi and naruto family fanfiction' could be that Kakashi accidentally stumbles upon a secret power within Naruto's family that has been dormant for generations. He then helps them unlock and control this power. Along the way, they form a stronger bond as a family. And as Kakashi is involved, he also rediscovers some of his own values and beliefs through this process.