I am preparing to migrated our Active Directory environment to be hosted on 2012 servers from 2003 and there is lots of information on this process on the internet. It seems easy enough, though not to be taken lightly. But to "cut over" fully, that is to shut down the old 2003 servers and point everything over to the new servers is a little more involved. IE DHCP services as well as point all static configured network devices to the new DC (also DNS) will take longer.
I would prefer to do this in stages, IE one week, get a few additional 2012 DC joined to the domain and replicating Active Directory and DNS services. Run that for a week to suss out any potential issues as well as not having to do too much all at once in one day (recipe for problems in my opinion). Then the next week, spend time migrating DHCP database to the new DC as well as updating the scope settings to point to the new DCs for DNS resolution. Changing all of the static network devices DNS settings and then having one of the new DCs takeover all FSMO roles.
First and foremost, does this seem like a logic procedure and am I missing any steps. I am guessing the new DC will pick up to use root hints as opposed to forwarders (which is what I want) from the DNS Zone replication data?
Second, will running 2003 with 2012 DCs in tandem for a couple of weeks cause problems, or is it ok?