Long distance parent visitation?

CPA04

It sounds like STBXH will be moving back to his hometown and in with his parents.  It is approximately 100 miles away from where we live (and where DS and I will continue to live).  STBXH wants EOW (and also a week at Christmas and 3 straight weeks in the summer...), but what are my responsibilities when it comes to transporting DS to and from?  I feel like packing up DS and driving the 100 miles there and back 4-6 times a month is not only inconvenient for my schedule, but with the cost of gas, it would get super expensive.  What sort of arrangement would you propose?

Also, STBXH does not have a driver's license.  How does that change your response (if at all)?  I want to work with the situation as it is, but not be taken advantage of either.  Input appreciated!