hanges I need to do in vCenter and ESXi when changing subnet mask

I am in the process of changing the subnet mask in our network from 255.255.255.0 to 255.255.252.0.
I already changed all our printers, appliances such as Barracuda device, fax server, firewall, etc.
I just configured a new class 3 managed switch with the new subnet of 255.255.252.  The ip for it I used one in the 255.255.255.0 range. I rather keep all my appliances on that same subnet mask value.
Now I am in the part where I have our esxi Hosts and vCenter and all our other VMs in our network that are statically assigned with previous subnet of 255.255.255.0.
We also run VMware view environment for half our users(eventually all users will have a vDesktop).
When is the process of changing the subnet mask in our environment without knocking our our network.

Also, our management in each host machine is on the same subnet as all our devices.
I was informed it is best practice to have our management port on a separate subnet.
What is the process of doing this?
I am clueless in that process.
Also, is it possible to share vMotion on that same subnet? Since vMotion doesn't get used that often.
Right now both management and vMotion share two nics ports.

Pls advice.