I have two Guest Passes for World of Warcraft, and two for StarCraft 2. If my friend makes a StarCraft 2 account off of the Guest Pass, does my WoW account get a mount? I do not have a StarCraft 2 account.
The only way I know of to get a mount from inviting other players to play is through World of Warcraft's Recruit a Friend service. You have to go through Recruit a Friend (which involves playing WoW) and your friend has to pay for a couple months in order to get the mount.
Those guest passes don't do anything for you, really; they just let your friend play for free for a while. Even if you did have StarCraft II, you wouldn't get anything tangible out of your friend using your Guest Passes (other than being able to play with your friend, of course).