Ya, if you could merge our networks, that would be great...

Network/AD merger

So we have been tasked to merge 2 separate networks in the next couple months due to relocation of employees and political pressure now that we are one company. The kicker is we need to have a new ad domain moving forward not either sides original domain. Site 1 is fairly small and has a single sbs2011 acting as their everything dc/fs/exchange 2010 site 2 is much larger with multiple DCs file and app servers and a single exchange 2010 server. Sites are connected via fiber.

My thought was to setup a tree domain at site 2 with the new AD domain and migrate site 1 to it setting up a trust relationship between that new AD domain and site 2’s original domain.Then slowly transition from site 2’s original domain to the new 3 AD domain. Is this crazy or is there a better way? Also how would exchange migration look from site 1 in this scenario? Any gotchas I need to consider?

Was trying to think about how the networking side of it should look as we are about full in our standard class c lan subnet. The idea was floated to change the subnet to allow more hosts but I was thinking about doing more something along the lines of adding additional vlans.

Thanks for any feedback