One idea could be that they face unexpected challenges during the pregnancy. For example, they might discover some health issues related to the baby and have to deal with difficult decisions. Another plot could involve their families' reactions, some being overjoyed while others are skeptical or even against it at first.
One idea could be that Sophie's pregnancy affects her magic in unexpected ways. Maybe she starts to emit a new kind of magic that attracts unwanted attention from dark forces. Howl then has to protect her and their unborn child while trying to figure out what's going on. Another plot idea is that they receive a visit from a mysterious healer who warns them about a great danger to the baby. This sets them on a journey to find a way to keep the baby safe.
Maybe they discover they're pregnant during a particularly dangerous job. This could lead to a lot of tension as they not only have to deal with the bad guys but also their new situation. They might have to make some tough decisions about whether to continue the job or focus on the pregnancy. And the rest of the team would start to notice their strange behavior and try to figure out what's going on.
A more dramatic plot could be that Lauren has some complications during her pregnancy. The family then has to come together to support her and deal with the stress. It could show how they all grow and become closer through this difficult time.
Another plot could be that Charlie and Harry are working on a special project together. During this time, they fall in love and Charlie gets pregnant. But there are outside forces, like a rival group that wants to stop their project. So they not only have to deal with the pregnancy and their relationship but also fend off the threats to their work and future as a family.
Charlie could become more in tune with his emotions. The impending fatherhood makes him realize his own feelings more deeply. He may also become more patient. Sophie might start to see the world from a different perspective. The fact that she is going to be a mother makes her more empathetic towards other mothers and children in the fanfiction world. She may also start to value the simple things in life more as she anticipates the arrival of her baby.
One possible plot could be that in an alternate magical universe, a spell goes wrong and causes both Bill and Charlie to experience some of the physical symptoms of pregnancy, while Hermione, being the brilliant witch she is, tries to find a way to reverse the spell. Along the way, they could have humorous exchanges about the situation and learn more about the magic behind such strange occurrences.
The story usually involves Howl's protective nature kicking in and Sophie facing various challenges during pregnancy. There might also be magical elements influencing the situation.
One possible plot twist could be that there are complications during the pregnancy. Maybe there are health issues for Sophie or the baby that require them to seek out rare and dangerous remedies. Another twist could be that their pregnancy is a result of some sort of magical interference that they didn't expect. This could lead to them having to deal with the consequences of this unexpected magic while also preparing for a new life.
One idea could be a story where Max and Sophie become friends with Ginny and help her navigate the complex social scene in the town. They could introduce Ginny to new hobbies and interests that are different from what she's used to.
A plot could involve a magical accident that causes Hermione and Charlie to swap some of their magical abilities. They have to work closely together to reverse the spell. During this time, they learn about each other's strengths and weaknesses and develop feelings for one another.