Good day,
Generally speaking, there's no problem if you have HA enabled on all your hosts. There are a few things to note, though, when designing an HA cluster. I highly recommend you and your VMware Administrator read the vSphere High Availability Deployment Best Practices, which can be found here
http://www.vmware.com/files/pdf/techpaper/vmw-vsphere-high-availability.pdf
Cheers,
Mike Brown