Race Change

I am considering doing a character race change from Night Elf to Human and I was curious how my mounts would be affected. I know that the Night Elf mounts I have are suppose to become the equivalent Human mounts, but what happens if I already have all of the Human Mounts and all of the Night Elf Mounts? I want to ensure that the end result won't be me losing all of my tigers even though I already have all of the horses. They can be expensive!!