How linking to other sites can affect my DA?

I'm working on a niche blog right now. The niche in question is a very low competition one, so I think that I can dominate it with the right link building strategy.

And I had one idea the other night. As my blog will be local focused and I'll talk about products on a narrow niche, I'm thinking about getting links from local stores. The idea is to approach them asking if they want to be "certified" by my website for free. I'll write a review about the website, add it to a special "trusted sellers directory" on my site and send them a branded "seal of quality" in form of a HTML snippet for their website footer, with a link for the review.

My question is: this "trusted sellers directory" will impact negatively my DA? Also: the links on the seals will worth anything for my website?

I just thought: if I NOINDEX the entire category of trusted sellers, would it prevent the loss of link juice?

You don't have to noindex such posts either the directory,
If you're really worried about that, add a nofollow tag to the links