You should call your credit card company to dispute the charges. While most hotel reservation agreements provide that the guest is responsible for any damage to the room, I have never seen an agreement that provides for a guest to pay for another's room charge under any circumstances.
The above constitutes general information only and should not be considered legal advice.
Definitely call your credit card company to dispute the charges.
I have never seen a hotel charging someone's room rate on to another guest's credit card!
If there was something broken inside of your son's hotel room, the hotel should have pointed this out immediately.
I think that here the hotel took advantage of the fact that your children are young adults using their father's credit card and are traveling by themselves.