you have 68 cores among your hosts
with 100+ machines coming in it might be good future proofing to use a resource pool with higher shares dedicated to your servers then your xen desktops
with expandable /unlimited reservations you should be able to work as if no pool was there if there is no contention.
The recommendation was always to keep the VDI and Servers workloads on sepearate Host Clusters. This way you would avoid any contention while keeping things as simple as possible.
While I'm sure that is the white paper "best practices" guide, they rarely apply to most cluster builds. If I had another $60-80k to drop on hardware and host licensing, I would go that route, but it looks like adding in a resource pool to keep servers and desktops separate would be a good idea.