In response to original post;
Personally, I do not see a problem with it. Perhaps this is because I am a Christian myself, but I can also see your concerns. I think the way you are presenting it, however, is very interesting; experiencing a death in the family, we often wonder why someone dies and another doesn't, and for a game sort of explaining to the person who did pass why I think is an interesting topic to explore, but you should execute it very carefully and also, prayerfully.
I myself have considered having God in my stories, though since mine takes place in a fictional world altogether, there are a few different rules but are all inspired in my Christian beliefs. For example, God has a different name but I try to make it obvious to which God I am referring to while also it can be seen as the god of that world (think how Aslan in Narnia said he goes by different names in other worlds). So that is one way to go about it, though I do applaud you for taking the more direct approach. Yes, there will be people who will not find it interesting or disagree, but in truth most people have manners and do not start flame wars (those who do typically are trolls). Besides, I have played many games or enjoyed many stories that had mythical gods or made-up gods, etc.! I feel stable in my faith for it not to hinder me, and I do not get offend, and I am sure it is the same way with people on the other end, so like I said, approach it carefully and prayerfully.