Can anyone recommend any good books which can be used to explain to younger siblings?
And at how many weeks did you plan to tell them?
I'm only ten weeks so no immediate plans to tell the little ones as frankly once 4 year old knows the whole world will know 
We have a 3.5 year old and 2 year old.
Any advice much appreciated.
Eldest was 18 months when youngest was born so we just didn't really do anything as such to prepare him as felt he was to young to take it in - obviously he is a lot older now and keen to handle it in a way which won't be a huge chock to them.