Windows Server 2008R2

I am looking for any advice or possible traps to doing the following network upgrades:  I have a single domain network with 4 remote sites.  I am tasked with bringing all domain controllers up to 2008 R2.  I have 4 remote AD sites and in two of those the dcs are already 2008R2 so the forest and domain have been prepped for that as well as for RODC.  My one concern is that we have several applications and all other domain controllers that rely on the IP address of the current role holder and first DNS server and DC in the domain.  I am using all new hardware and will dc-promo a new 2008R2 server and seize all FSMO roles for it.  I would like it to take over as the main DNS and DHCP server with the IP of the older server.  I assume doing this overnight and then releasing all leased IP addresses is my best option.  Any advice on this process and input on whether backing up the DHCP database from a 2003R2 server and restoring it to a 2008R2 server would work is appreciated.
Thanks