Migrating web sites from Windows 2003 to Windows 2012R2

Hi,
 
 I have several websites running on Windows 2003 Std server (Computer Name: IIS, 192.168.1.4). I just set up a new web server on Windows 2012R2 (Computer Name: IIS2, 192.168.1.146) and I need to re-create all those websites on this new server.
 Currently port 80 is forwarded to 192.168.1.4.
 Other than creating one website one at a time on IIS2, are there things that I should be aware of?
 Are there any shortcuts? Easy migration method that I can take advantage of?
 
 Also what would be best way to compare page by page as I create new websites on IIS2 that they look exactly the same as they look on IIS? I know that I can change port forwarding from 192.168.1.4 to 192.168.1.146 each and every time I need to view the website, but then I have to change it back whenever I am done.

There are users out there on Internet who place orders online from morning to late night.
 On Weekends, it would be much easier because I can tell the users not to submit any new orders online. But weeknights are kind of difficult unless I stay up until late at night to begin my work.