Yes, this is supported by VMware when all of your devices and disk controllers are on the vSAN compatibility list. No problem. Although of course you need to realize that there could be a performance difference between these servers as well for your data and your VMs. So depending on the workload, this may, or may not be noticable.
Seconded. You are good to go with the mentioned setup. And yet expect performance drop on the third old host.