IF they ask respond with, give me a bit of time to think this over. And leave it at that. ...then wait until they ask.

I think you are worrying yourself for no reason here. Any family that chooses to drive that long, when they have other closer, easier options has made their decision because thy value your service. I don't think they would ask for a break on fees.

If they do, look at how it will impact you and make a decision. Again, I don't see them asking for a break on fees...if the weather truly poses a problem then they may seek care elsewhere because the length of travel is truly too much...but that is out of your control.