How much of the background needs to be exposed correctly? A different option from a stronger light (which may mean many strong lights to avoid falloff from one side in a family shoot), would be less light... Use a scrim to reduce the amount of sun shining down on your subjects or background.

Searching on B&H, they only call them scrims up to 4' x 4'... after that, they call them butterfly fabric. They can get expensive if you go really big, but they seem affordable at reasonable sizes. A 4'x4' 1.6 stop scrim is like $100, and an 8' x 8' is $150 or so, and a 12'x12' is around $200, a larger 30'x30' 1.6 stop butterfly fabric is nearly $1000... That sound expensive, but whatever lights you'd need to evenly light a 30'x30' space would be far, far more than that.

I'm not a lighting expert by any stretch, nor do I know your outdoor typical setup. These might not work you for at all. Just pointing out a different option than adding a bunch of expensive lights.