Tips on cold e-mailing product reviewers?

I've built with my wife and friends an Online Escape Room (https://elevenpuzzles.com). So far we're getting very positive feedback, so we plan to e-mail reviewers hoping they'll enjoy and review our game.

Any tips on what to do and what not to?

We selected reviewers that we think might be interested and enjoy the experience. We don't want to force anything. Obviously, we also want the reviews to be honest, negative feedback is welcome.

And what about giving away an access code for free? Won't that skew the review? What's the common practice?