We migrated our DHCP server using the steps in this article:
Your steps look good, but I would modify it like this.
1. Add to DHCP role to the 2008 R2 server
2. Use the right-click 'backup' option on the 2008 server and backup to a folder on the network or the new DHCP server
2.1 Stop DHCP service on old server
2.2 Disable DHCP Service on old server (Most users should have existing leases and not be affected during this short period.
3. Restore the backup created above on the 2008 R2 server using the right-click option in the MMC
4. Authorise the 2008 R2 DHCP server
4.1 Immediately test with a workstation running ipconfig /release, ipconfig /renew
4.1 Go the DHCP server properties Advanced, and select Conflict Detection Attemps and choose 1. This will resolve any conflict issues, even though you shouldn't have any. I beleive that you can right click the scope and verify as well after restore.
Also, Please remember that if the address of the DHCP server is changing you may need to adjust DHCP relay or BootP forwarding on your routers.
Now that the old DHCP service is stopped and disabled is it good enough to remove the DHCP role as I don't think we can deauthorise it cleanly when the service is stopped unlike the final post suggests.
How can we cleanly and safely tidy up the old DHCP role without messing up the new one?