Hi SS
In my eyes its going to be difficult for you to achieve a nice vCloud environment with only 3 hosts.
Normally you would have your vCloud management VMs (VC, VCops, Trend Micro, Chargeback, Cloud Cells) etc hosted on there own cluster away from the hosts that you would be using for the Cloud resource.
If you want to factor redundancy in for these then you would need atleast 2 and 2, so 2 hosts for management cluster and 2 for vcloud resource.
Obviously depending on your requirements and usage you may get away with a 1 and 2 split.
For the purposes of trend micro and vshield you certainly want to seperate the hosts out from the resource vm cluster being managed by them as I dont think its supported to run the VC on the same host as is being managed by the Trend Micro anyway?
Hope this helps 