AFAIK you only need to notify a benificiary what they themselves have inherited, but ultimately the Will becomes available to the public after probate. Personally I gave a copy of the will to each person, but it was all very straight forward and equal. I can understand why you may not want to disclose all the details if it is likely to cause rows.
There may be other issues if they are entitled to a certain % of the estate if they are a wife or child.
I'm sure I'll be corrected if I'm wrong