Extract beers rarely have issues with mouthfeel. The maltster most likely cut the origin grist with some carapils and crystal malt, and then mashed in the mid 150s (F).
Avoid adding simple sugars to your fermentables. And try to get ahold of unsweetened coconut flakes from a place like Whole Foods, or a specialty supermarket. An abundance of simple sugars in your extract porter will not help your goal for a creamy mouthfeel.
Whatever you do, don't add starchy adjuncts to your extract beer, like flaked oats. These must be mashed with the proper amount of enzymatic base grain for conversion.