[bojan]

In a typical binary system,stars are from light-hours to light-days apart.
Alpha Centauri:
A & B are couple of hours apart and the orbital time is ~80 years.
Proxima is 13 light-days away, orbital period in excess of 100.000 years.
You can use Kepler'd laws here they apply perfectly, to verify the consistency of those numbers.
So you can see, the gravity propagation is irrelevant.
What is not relevant is the influence of components A & B to eventual planets in a stable orbits around them.
Or, in our case, Sun-Jupiter system, and inner planets (the influence of Jupiter and other bigger planets to smaller ones and vice versa is called "perturbations" and this influence is fully accounted for... otherwise we would not be able to calculate the planets positions couple of thousands of years in the past and in the future. (Even the light pressure from the Sun's illumination is taken care of in attempt to precisely calculate the orbits and positions of asteroids..))
This is called "n-body" problem.
Again, no need to take gravity propagation into account. Have a look at wiki.
Also have a look at any celestial mechanics book (Meeus perhaps?)