We have no idea where in the country you are or what your zone is, but I would start by planting trees along the yard perimeter for privacy.

In addition to "privacy and entertaining space" can we presume that you will also want to enhance the yard/house by improving the appearance and views with plantings? If so, we'd need to see the complete back house face, and the outward looking view (toward the property line) from the most likely patio location, which would be just outside the back door. For the latter, place the camera outside the back door and begin by aiming toward farthest left. While remaining in the same camera position, continue panning/pivoting the camera, taking slightly overlapping shots until you have captured the far right view. The house will show in the first and last picture. To capture the house, move the camera to the property line, in line with the center of the house, looking back at it. Take pictures that begin at the left side property line. Continue panning all the way to the right side property line, with the house in between the starting and finishing point. All of this can probably be dine in about 7 or 8 pictures.

Describe exactly where the back lot line is (per something visible in the picture.)

Thanks for the comment. I'll try to get these pictures and post them for more insight.

Pictures as requested. To your question, we definitely do want to enhance the yard appearance with plantings. We particularly like evergreens for the added privacy throughout the year.

Nice blank slate! I would start with paper and measuring tape. Get some graph paper with 1/4 inch squares and draw on the property lines and the house. Starting at the back door draw on where the patio or deck would be, allowing for generous space...where would the grill be, the table and chairs, extra seating, walkway from front yard into the back. From there you can see where your need for privacy is most important, you might need some pretty tall trees to get any privacy to that back house, so you might be able to create a more private space closer to the patio.

Were does the water go from the swale? Has there ever been problems with water in your basement.

Here are some general ideas ... not about specific plants, but about ways to arrange things. Follow the advice about creating a plan on paper and adjust everything as you work out the details.

Thank you for the design idea! I like the evergreens along the back of the yard. Do you see any benefit of planting any tree that would eventually provide a canopy on the backside of the yard? Another detail, the backside of the yard points to the southwest.

I also spoke with the builder about the rocks they used for the dry creek. I can purchase additional boulders of various sizes from a local distributor to widen it and to mix in various sizes.