A popular choice could be Lightning McQueen. They have a close relationship in the Cars universe, and it would be an interesting dynamic to explore with them as parents.
In a more emotional plot, Sally could be worried about bringing a baby into the world of racing, fearing for its safety. She has to overcome these fears with the support of her friends. She could also be thinking about teaching the baby all about the history and values of Radiator Springs when it grows up.
The Tensura web novel follows the story of Rimuru Tempest. He starts as a normal salaryman in Japan but is reincarnated in a fantasy world as a slime. Rimuru then begins to build his own nation and gathers various powerful and unique beings around him. He also gets involved in many power struggles and battles against other strong entities in this new world.
Personally, I think both have their own merits. The Tensura manga is great for those who are new to the series or just want a more straightforward visual experience. The panels are well - drawn and can easily show the progression of the story. On the other hand, the light novel is a treat for those who love to get lost in detailed worlds and complex character development. It allows you to use your imagination more as you read the detailed descriptions. So, it's really a matter of whether you value the visual aspect more or the detailed written content more when deciding which one is better.
Some local libraries might also have the Tensura novel in their collection. You can check their catalogue and borrow it if available. Additionally, there could be some fan - made translation websites, but make sure they are legal and reliable sources.