Last thing that I want, as a parent, is to have another adult, a stranger, an authority figure, to advocate on behalf of my child. This would definitely set me off. Big time! Is the guidance counselor planning to pay tuition and all other expenses? No?! Than, why is she in position to argue with the parent?
Talk to you parents directly. Find some selling points. Apply to Harvard, common. If you are accepted, you may change your view of Ivys, if you are rejected - your parents would appreciate that you tried 
If you really like some college, find something that is valued by your parents and that may be used to sell this college to them.