dd (2.3) will be a big sister in February
we told her, yes, obv, and she came to the 20wk scan 'to see the baby on television' etc
we have been to visit friends with new babies, talked to her friends about their new siblings, met other pg mums who are further along etc
but having the books about (none of the aforementioned, they are all 70s and 80s ones from my own childhood) gives her a chnace to look at what it migth be like in her own time and on her own terms. She also uses them as a cue to get us to talk to her about the new baby.
I found 'Sophie's Baby' a bit dark tbh - atm I want to big up the positive aspects of it rather than make her worry about being angry / everyone beign busy etc in advance.
The best one we have is called 'My Brother Sammy' (no not the one about the autistic brother, tis an ancient 70s one where the dad has a porn star tache) as after the big tummy / granny comign to stay / mummy in hospital / bf and nappies scenes, it finishes with the baby asleep in the basket and Mummy, Daddy and new big sister Mara having pizza for dinner together, which is always a draw for dd .