Upgrading an Active Directory Domain from Windows Server 2003 R2 to Windows Server 2012

hi guys

i have Windows 2003 R2 Domain Controllers ( forest Functional Level - windows 2003 )- 2 at Main Site and one at DR site. also has Exchange 2007 Sp3 with HUB/CAS Servers & Mailbox(SCC) for DR( SCR ).

planning to upgrade AD from windows 2003 R2(FF-windows 2003 ) to Windows 2012(FF-Windows 2008 ) & Exchange 2007 Sp3 to Exchange 2010 Sp2 .

as i found, Exchange 2010 can't be installation on top of Windows 2012 OS until Exchange 2010 Sp3 released . So planning to installation Exchange 2010 SP2 on top of windows 2008 R2 Sp1.

But my quotation is , i am planning to do the AD Migration first and Will the Exchange 2007 Sp3 will support for Windows 2012 Domain Environment( even if i keep the forest functional level to Windows 2003  on Windows 2012 Domain Controllers).i may can keep additional Domain controller (windows 2003 DC) and FSMO roles will be on Windows 2012 DC.

or is it better to upgrade Exchange 2007 Sp3 to Exchange 2010 first, then the AD.( since exh2007 SP3 may not supported for Windows 2012 Domain( even if Forest Functional level  window 2003 )

Since this is related Exchange 2007 SP3 Supporting Issues. i posted on Exchange Forum(couldn't find Exchange 2007 and posted on exchange 2010) .  i found these articles. but  it's didn't give answer my to question.

http://social.technet.microsoft.com/Forums/en-US/winserverDS/thread/caf4c5e8-28fd-461a-8f9c-190a0b6ef7b0

http://social.technet.microsoft.com/Forums/en-US/winserver8setup/thread/f5eabb78-802b-4bd1-8008-e71c3da5f70e

Thank you

indunil