(a) You're too close to yourself to see what makes you unique.
(Unless, that is, you're using a process similar to one I lead you through in Dream Job Formula, which is designed to uncover your most valuable talents, signature strengths, and personality traits.)
(b) Your daughter (or son) sees you for who you are at your best. They depend on you. They look up to you. Chances are, they'll do a better job of promoting you to hiring managers and recruiters. After all, they don't judge you with the same critical eye through which you judge yourself.
(I know it seems hard to believe sometimes. But if you think about how you would advocate for your kid(s), it shouldn't be too surprising that they could return the favor. Back when I was a teenager, I was a BRAT to my parents, especially my mom. But I always admired her a lot and I looked up to her and my dad.)
Anyway...
If you wanted to be a little crazy, you could try sending in your resume to a few positions with this new cover letter -- signed by your daughter.
Depending on the culture of the organization you're applying to, it might go down well. It will certainly stand out, and some might view it as creative.
But, personally, I won't do that.
Here's what I'd do:
Rewrite it with your own voice. Chances are, this new cover letter will feature some "qualifications" you wouldn't have given a second thought to. I'm sure if you told them a little bit about the position you're applying for, you might be surprised at what they create.
Give it a try -- and let me know how you get on.