Given parameters:
Fraction given to charity =

Fraction given to wife =

Unknown:
Fraction given to son and daughter =?
Solution:
Let the total property = x
Fraction given to charity =

Fraction given to wife =
The remaining was given to son and daughter = F
So;
Total property = fraction given to charity + fraction given to wife + fraction given to son and daughter
x =

F = x - (
)
F = 0
The son and daughter will not inherit anything