We have about 7 or 8 Macs on our network as well, and out of all the products that we tested we found that http://www.thursby.com/products/admitmac-eval.html to be the best solution for our needs.
It allows you to join Macs to AD and somewhat resemble behavior that of a pc on the Macs, it even allows for some scripting for logon mounts, printers, etc.
Windows share (cifs/smb) permissions are respected for the most part unless you have funky settings traversing different directories, but I would do some testing before implementing, since SANs tend to behave different.
Let me know if you want me to send you more info on how we do things here.
Have fun,
Rolo Clavero