Questions about donation

When we filled out our paperwork for IVF, my husband was adamantly opposed to donation of any sort. He believed that we should use them or destroy them. We only used one and don't plan another pregnancy so we have another 3 left frozen.

Since then, one of my best friends began her search for donor embryos. Seeing my friend had opened my husband to the idea of donation. But I don't know how it works.

Does the fact that we used donor sperm make this an impossibility? I have no idea of the legal issues. Is it too late to donate them given that it wasn't in our original paperwork? How do we donate if our clinic doesn't offer services? Is there any interest in biracial (Mexican & white) embryos? How much flexibility do we have in setting terms? I would want to know if anyone had a successful pregnancy with our embryos and would want to be alerted to any health issues.

Thanks!