Dont listen to the advice of others it will drive you insane hahahahhahhaha

follow your nose, learn your nursery rhymes and buy lots of books to read together.
Try not to push your eldest away when attending to the newest member, let them help and join in, even if your BF take that time to read a book. We use to sing about anything...
Best singing voice

Ohhhh look at Tankkk drinkinggg his boobie milk.......he looks happy
Look at his big sister next to me...she's going to help me change his nappy

I know stupid but she thought it was a hoot

oh and when all else fials, wack them in the pram and go for a nice longgggg walk..it helps calm the nerves