Not sure how much time you have to prepare, but if you can go into the meeting with some initial numbers on the ongoing costs it will take to support the Macs in your environment, that might help. For example, say you now have to spend 3 hours per week dealing with Mac specific user issues that you didn't have before, add that to the list with a cost estimate. Patching? AV? Security issues? All of them should be quantified and presented to management when talking about the ROI for the new machines.
YMMV, Chris ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
