As mentioned above "Define a budget that you and the customer can work with."
A rather low budget solution........ my $.02...... Elevate the existing tree limbs up. Remove any of the miscl. scrub in the natural beds. And most of all create a smooth definition between the turf and the natural bed using large flowing radii. Might need a bed trencher/spray with non-selective herbicide or flat just edge and dig it out. Looks to be like some Day-Lillies and Juniper already existing. If you need plant material to fill some of the void areas, just repeat these in group settings(mass plantings). Lastly mulch with straw. It's a natural area, you want to create an area that is within the drip line of the more mature trees to catch the debris that falls from them to create a low maintenance yet crisp landscape feature.