I know this is not directly related to B visas, but usually, with the VWP if you overstay and it is of no fault of your own, you are still in overstay (hence why it is always advised to never stay the whole 90 days, but to plan for a 86-87 day trip just incase of flight delays etc.
However, in light of this situation, USCIS has set up remedies to grant VWP entrants another 30 days because of the HUGE scale of this natural disaster. So USCIS is aware of the effect this situation is having on travellers (both VWP and other visas-B visas included) and are taking steps to help visitors out.
http://ukinusa.fco.gov.uk/en/news/?view=News&id=22076854
At airports, U.S. Customs and Border Protection (CBP) may grant Satisfactory Departure for a traveler whose VWP admission is expiring and who is unable to depart timely as a result of airport closures or flight delays/cancellations. If the stranded traveler is not at an airport but elsewhere in the country, the traveler may apply for Satisfactory Departure from the local U.S. Citizenship and Immigration Services (USCIS) office. If granted, Satisfactory Departure allows the VWP traveler to stay in the United States legally for an additional 30 days. If the beneficiary leaves within that period, he or she will not be considered to have overstayed. Both agencies have provided their staff with guidance on the applicable legal authorities under the VWP in circumstances such as this.
Persons traveling under a visa should contact the nearest U.S. CIS office and follow the instructions on their website. While this link recommends initiating the process 45 days in advance, U.S. CIS is providing reminder guidance on how to handle such cases this weekend.
This is direct posting on the British Consul website....the part bolded would be applicable to yourselves so you should go to the USCIS website and follow the instructions there.