Well I am currently working alongside a large amount of Federal employees, about 50% are being paid.  

 They do have things like letters to creditors they can get about the shutdown, and most creditors provide an alternate solution to owed payment even though there is zero requirement to do so.  

 But to say they can go on "vacation" is a sign of severe disconnect as most vacations are pre-planned and are term based.  Since at any time many of these workers are expected to return to work they can not just go on a "vacation" unless "vacation" means staying within 1 hour of their post, not consuming alcohol and leaving their family at home.