Jambalaya experts:

I'd just wake up a bit earlier and cook it so it's done right before leaving for church and it will stay hot for a while, assuming you're cooking a good bit of it.

Reheating in the pot may make it become more gummy or worse, scorch it if not stirring it often.

OR, you could have your stock and all the ingredients cooked beforehand and add the rice right after church lets out. It really doesn't take all that long for the rice to cook, and that way it's all hot and fresh.

Agreed. You can fry meat and onions and then and liquid the night before. Then after church, heat up and add rice.