How to prove or demonstrate to the Ivy's that I am a varsity level athlete?

IMHO I think you are going to have to enter some tournaments that will award you for your achievements. That would be proof of your excellence in these sports. Otherwise, you might try a letter from your coach. In America university scouts will often come to your school to see you in action. I don't know if you are simply looking to sports as a way of enhancing your application, or if you are looking for a sports scholarship. There is a big difference.