I am in the beginning process of migrating to Windows Server 2016 and this morning I decided to tackle migrating my DHCP server from 2012 R2 to 2016. This is actually quite an easy task so nothing to be afraid of. All it takes is two PowerShell commands.
The first is this one:
Export-DhcpServer -File C:\DHCP\DHCPData.xml -Leases -Force -ComputerName FQDN.2012.Server -Verbose
The second one is this one which is much like the first:
Import-DhcpServer -File C:\DHCP\DHCPData.xml -BackupPath C:\DHCP -Leases -ScopeOverwrite -Force -ComputerName FQDN.2016.Server -Verbose
It is simple as that and now you can remove the DHCP Server role from the 2012 server and decommission it.