Ghost Recon should run fine as long as everyone has the same Ghost Recon version. The latest is version 1.4. The Mac patch which includes GhR 1.4 is version 1.0.1. Aspyr has available patches 1.0.2 and 1.0.3 but the GhR version is still 1.4. I'd recommend skipping the 1.0.2 patch and installing the 1.0.1 then 1.0.3 if you haven't patched the app already.
Raven Shield will not support cross platform networking. Apparently, the netcode for Raven Shield can't be ported for some reason. Since Raven Shield uses the Unreal engine it would make sense that the Mac and PC versions could play against eachother but it seems the netcode was fubared enough so that it isn't possible. maybe the replaced it with code that requires DirectPlay. Whatever the reason, many were shocked by the news. It was confirmed by Glenda Adams of Aspyr. As a former programmer, if she couldn't see any solution to the cross platform netplay, then the netcode must really suck.