Thank you for your response.
There is no set rule / law in relation to pick up and drop offs.
If a court was to adjudicate on the travel - then courts often make the decision that the travel should be split. Usually it would be the person picking up for the commencement of their time ie the mother collecting and the father picking back up. This is often seen as fair. There is quite a distance involved and therefore I am inclined to say that a court would adjudicate that this should be split.
Whilst I note that it was not part of your original question, I do note that the mothers home has been described as a hostile and volatile environment. Whilst I do not know the specific details, it is important that your husban's son is safeguarded. At 12, he will be able to communicate what is happening. The courts do consider that both parents are equal and it is a child's right to a good relationship with both of their parent, but this is subject to the proviso that it is safe to do so.
If something was to happen, you might have to consider referring to social services to make sure that the child is safeguarded.
Mediation is worth considering, if matter remain somewhat amicable. This might help resolve the pick up / drop off issue without the need for court.
Positive feedback is gratefully received. Once you have left positive feedback your question remains open and I can answer your follow up questions for free.