10.3.9 Server OD, AD and Exchange

We currently have an Xserve running 10.3.9 with OD setup. The server acts as a PDC for our Windows machines that autenticate against it. All windows and mac machines uses local accounts/profiles.

We are now adding a Windows Server 2003 running Exchange server into the mix. Exchange requires AD. I’m not sure how I want to go about this yet.

Idea 1- Set Windows Server 2003 as DC with GC running Exchange. Setup OS X Server as domain member and have it pass autentication through active directory?
Idea 2 – Setup a seperate domain just for exchange?
Idea 3 – I wish I could add the windows server as a member server to OS X Server but there would be no AD

We want to be able to manage user from one location, whether it’s AD or OD doesn’t matter. The biggest thing is we want single sign on. I

Does anyone have any ideas or a similar setup?
If I setup OS X to pass autentication to the Windows server how will that affect our macs?

Thanks!