I agree with David and want to make you aware of an interesting opportunity: Once the baloon driver is installed in these VMs you will be able to force balooning on them by setting a RAM resource limit that is lower than the amount of configured RAM. That means e.g. you could limit the 32GB-VM to 24GB (or even less), and the baloon driver will steal the surplus of 8GB and return it to ESXi.
Of course in production you should use this method only as a last resort, but there is a chance that the VM admins will even never notice that. In the past I tried that with some heavily oversized Windows/Exchange servers that were in test status, and the admins were not aware of a problem until some day they really started to use the system ...
- Andreas