Re: running Virtualbox from the icon
It is possible that you've made things more complicated than they need to be. There is no need to run VirtualBox from a terminal using sudo and it is actually unwise and insecure to do so. Never use sudo for anything except system administration tasks. Are you doing this because you cannot launch it from the graphical VirtualBox Manager under your own account? If so, this is likely due to the fact that you did not add yourself (or your wife) to the vboxusers group (VirtualBox will only work for members of this group). To add yourself, do:
where "username" is your username. If your wife logs on under her own username, you will need to repeat this step for her as well (while running in your account, not hers).
sudo usermod -a -G vboxusers username
Once you've added yourself to the vboxusers group, you will be able to launch any virtual machine you like directly from the graphical VirtualBox Manager.
Creating an desktop icon is rather more complicated. It requires you to invoke the command line version of VirtualBox manager with the desired virtual machine as an argument. Let's leave that to step 2. Let's solve the immediate issue first and get you launching easily and securely. Let us know how it goes.
Newb: How far must I jump to clear the ledge halfway down?
Guru: It's bad to jump off cliffs. Let's look at better options.
Newb: Stop harping about "best practices" and just tell me.