I got a Mystic Tan a few years ago. It was okay, not great. They told me it was safe to breathe during the "shower", but it wasn't comfortable breathing in the mist, so I held my breath. They had me put vaseline on my fingernails and toenails so they didn't get stained. They also told me to watch how much of the mist gets on the upper forehead/hairline area and to make sure it doesn't get too dark. My initial tan was okay, but it faded unevenly.
I'm pale and cannot get a good natural tan, although I don't even try that anymore since it's not healthy. I use Clarins Self Tanning products, which are the best I've found so far. Personally, I wouldn't do the Mystic Tan again. It may work well for some, but I didn't like it enough to go back. It may have improved since I did it, though.
Since you have about two weeks, it may be a good idea to try the Mystic Tan or other tanning product very soon so that you'll have time for it to fade if it doesn't turn out...and if it does turn out, then you could re-do it for a darker tan. Before doing any self tan, it works best if you exfoliate and moisturize the area the day before. Of course your ankles, knees, elbows and knuckles tend to be drier and absorb more of the self tan product...so they need extra moisturizer beforehand, so they don't get too dark. I've heard that you can use rubbing alcohol to remove a bad self tan...but I don't know if that works.
Good luck!