...you are going to have to violate some security policy (given the set of constraints that you've posted)...so someone in Security (or the AV guy) is gonna have to deal with a little infringement.
You need to remotely access 500 machines...or manual touch 500 machines and you need to do it with admin rights or the remote software available from the antivirus vendor.
There's not alot of other options...except leave them all broke and get whacked by the next virus to come along.