It sounds as if the keys are both worn and miscut.  We would advise getting the code from a front door lock, and sending it along with a photo of the key.  We'd then check that the code matches the existing key.  If it did, code cutting a new key will probably solve the problems.  It's been posted to lube the locks with TriFlow.  That is one of the best lubes for the lock, though here in the shop we use a special synthetic grease made just for locks.  I'd also clean the lock before the lubrication with carb cleaner, then work the key in and out, then flush again.  This will get a lot of the trash out of the lock.  I wouldn't do that to the ignition, however.  The grease that VW used in the locks originally was nearly as thick as wheel bearing grease.  When it combines with dirt and grime, or worse yet graphite, it turns to mud.  On some locks, we've literally had to use a hammer and a punch to remove the wafers.  DON'T USE GRAPHITE IN THE LOCKS!!
 
If by chance the code does not match the key, chances are very good that the key can be "sight read" and the correct cuts determined by the photo, and a correctly cut key generated to try.  As you say, worst case scenario is for the van to be sidelined for a few days and the locks sent off to a reputable locksmith familiar with VW locks to be rekeyed or overhauled as necessary.
 
Chances are, though, that a combination of cleaning, lubrication, and a correctly cut key will solve the problem.
 
Steve Sandlin
Registered Locksmith
84 Westy, 00 New Beetle, 79 bus, 74 412