Singing/performing nerves

The 9/11 1,100 sq foot memorial tours Minnesota for the first time in Waseca on 7/16. I'm singing the national anthem there, because the guy who arranges the performer is friends with a family friend that told him I sing well. He signed me on without even asking to hear my voice. So I recorded me singing it and PANICKED. I sound SO horrible for this song and now I'm freaking out. My dad says I sound fine, but he's my dad. I've never had a confidence issue with my voice before. Tips preparing/practicing? I'm so nervous now:(