I can't change EVC mode on an existing cluster, seemingly because my VMs are powered on... but the VMWare documentation says you CAN:
Change the EVC mode for a Cluster
"To raise the EVC mode from a CPU baseline with fewer features to one with more features, you do not need to turn off any running virtual machines in the cluster. Virtual machines that are running do not have access to the new features available in the new EVC mode until they are powered off and powered back on. A full power cycling is required. Rebooting the guest operating system or suspending and resuming the virtual machine is not sufficient." -- taken from VMware vSphere 5.1
So is the documentation from VMWare WRONG?
This is going to be a real PITA.