The easiest way to look at time dilation is in terms of an energy balance; energy conservation, and not in terms of relative reference.

For example, in the twin paradox, only the moving twin ages slower. It is does not matter if the stationary twin pretends he is the twin in relative motion. It is all about who has the actual energy; energy conservation. Only the moving twin had actual energy, added as rocket fuel, for propulsion. Therefore only that twin will show any tangible time dilation. The stationary twin does not age because his energy never changes based on energy conservation.

As a useful analogy, consider the relative reference workout. In this weight loss workout, you sit in the middle of a running track and watch the runners run around the track. In this workout, all you do is pretend you have relative motion. This allows you to burn calories and lose weight while sitting. Most people can intuitively sense this will not work, because energy conservation will trump relative motion. The burning of calories; time dilation, cannot occur unless there is an actual energy expenditure; conservation of energy.

In your example above, if both rockets are the same and used equal energy and move at the same velocity, they both will show the same time dilation everywhere along their flights. The time delay for signals from each ship to reach each other is not relevant to their energy balance. The signal between tends to confuse the issue.

Note:

Kinetic energy is 1/2MV2. Kinetic energy will square the velocity. The squaring of velocity has the impact of normalizing the vector; direction of the velocity. It does not matter if the object is coming or going, since the kinetic energy is only dependent on the scalar of velocity and not the vector. There will be as much time dilation in an expanding or contracting universe, if both have the same velocity.

On the other hand, from earth, an expansion scenario will show a red shift while a contraction scenario will show a blue shift. This will alter the apparent energy balance of the universe, even though there is a constant time dilation. The confusion is a connected to the earth being used the zero state of energy; relative reference workout.