I'll try to give you a few suggestions, as I feel I understand what you're asking for.
The best way to get differentiating Scattered objects blending well yet controlled by specific areas is to separate your initial large area into smaller groups.
Start with the large area and turn it into a group and then use Bezier Spline curves or arcs to create smaller groups from areas carved out of it... you can let these overlap so that the scattered items blend into each other. The Key Word here is "Groups" - select the areas you want to Host the Scattered objects and turn them into groups. Make New Render Lists using the Render list tab for each of these groups
So, you could create the dirt driveway you want to lead up to the house by simply creating that area, giving it a base dirt material and selecting it, then turning it into a group to use as a Host in a New Render List. Select items like gravel, sticks, loose leaves, etc. as the Scattered objects and the dirt driveway area group as the Host. Do the same with smaller areas for the dirt patches under the porches that you described.
Lastly, experiment with Density Falloff and Scale Falloff to get the blends looking the way you want them to.
Take a look at the example image... Good Luck!