Frankfurt AM Airport to small town on Lahn river (Nassau) - avoiding train

Hi All-

We will be landing in Frankfurt on Tuesday and I don't want to bother my family while they are at work to come pick us up. So my husband was thinking we should rent a car- any suggestions?

I looked up the train - seems mildly annoying, but not bad. He is less keen.

What would you suggest?

Thanks so much!