Is there a specific reason you want to use a "special" macro for this on your main instead of making a macro on each toon? I use a mount macro that sets my camera to a default view every time I mount up. I have this on a simulated X-Keys layout using Domino. The action bar button is bound to the same key on all toons so that when I press that key they all mount at the same time. I have the same setup for land and flying mounts. I also have a key bind set up to dismount using WoW's keybind menu so that if for some reason some toons are mounted and some aren't, I can quicking hit dismount and then mount to get them all mounted in a split second.