From the FAQ at the Park website's "Camping at Assateague" page:
Are generators allowed?
Generator use is prohibited during quiet hours 10 pm- 7 am. Outside of quiet hours, generators must be operated at a sound level that is not annoying or disturbing to other park users. You may be asked to turn a generator off or limit use based on sound levels. Failure to comply may result in a citation. (COMAR 08.07.06.20)
Another potentially important point - the $10 Maryland Lifetime Senior Pass is offered to out-of-state residents, too. Good for half-price camping Sunday - Thursday, as well as day use admission to Maryland State Parks.