I try to use natural sweeteners in all my recipes and cooking nowadays. And I've found that I normally can get away with fruits as sweeteners. For my muffins I'll just add lots of raisins or dates. Dates blended up work wonders. They are super sweet and sometimes we just eat one or two after dinner as our dessert (or a prune or something). The key for including them in things is generally to take out the pit, soften/soak in water, and blend up or chop finely.
Here are a few things I put dates in...
Sweet potato topping with pecans
But/date pie crust
Almond milk or smoothie/shake