There's a very easy way to accept and "win" the challenge in Mormonism without having to do very much at all.
The Mormon outline for the plan of salvation places everyone who dies in heaven by default, and builds a heaven that is multi-layered, while Hell is only really detailed as a single layer of concept (think of Dante's Inferno flipped upside down).
As long as you're not someone like "Hitler" (and some LDS even debate this), you don't just jump straight to hell.
Here's an image map to the LDS plan of salvation:
http://www.scripturecompanion.com/Downloads/Plan_of_Salvation_color.jpg
Notice how many lines go towards good stuff, and how only really one line goes to bad stuff (notice that even the first round of "bad stuff" even has a route out to "good stuff").
Then take note that all lines off of Earth start heading toward the good stuff (by a 2/3rds majority).
That's because the LDS position is that you have more than this Earthly chance.
So, the atheist position to LDS really can validly be:
"I'm good. I'll just wait for the afterlife to see God's world and make my decision then."
The only real solid reason to be LDS, aside from wanting to be LDS, as an imperative is if someone wants to attempt to be up in the third celestial kingdom.
If you don't care about that, and just want a decent afterlife party, then you don't have to lift a finger really.
Heck, they can even baptize you after you die just in case you didn't do that before kicking the bucket; just in case you decide to try for an upper floor office in heaven instead of the mailroom gig.
BTW: all of this is because of that starting point of premortal existence and that veil.
LDS holds that we all started out in heaven and knew God fully, and that we all picked our parents and our lives with their sufferings and rejoices.
The veil makes everyone forget everything they knew before being born mortally, and the mortal existence is needed to gain perspective (I'm really paraphrasing a lot of information here) which aids in getting a better seat in Heaven later (really important if you want to help other worlds by being their gods, but no one is supposed to hope or want that; just supposed to be accepting of it if tasked with the responsibility of being a world caretaker: "god")...
So...yep.
Unlike a lot of other religions, LDS is very easy to accept without accepting it.
You can actually, and validly, state that you chose this life before the veil and that you are supposed to be an atheist in this life before going back to heaven where you were too loyal to god to properly judge morality accurately and with the right empathy.