Bobcat or a compact TLB is what I would recommend. I would stay away from Dingos as I think of them as niche equipment. Great for jobs that require equipment in a confined space like a water feature or sidewalk demolition. They too skid like a bobcat so it will scuff the yard at best. Then consider grubbing with a dingo: will it not be fun. An option to explore to minimize yard damage is drive the bobcat near the house where your beds will be. Dirt furthest point and work backwards. Your helper will spread dirt for proper shape. Be aware heavy equipment and vibrations could negatively affect the wall at the stairs. An alternative to the above is pick few as possible spots in the yard that will be designated turn spots. From each turn spot you will either straight and slight curve to the next spot or straight line to the dump point. This leaves you with less yard repair work. Another option is rent an all wheel steer bobcat. The fancy $65,000 ones can lock the rear wheels and steer with front as if it were a tractor. That leaves compaction as the main concern which will be heavily dependent on soil moisture. My platinum pick is a compact or subcompact TLB. Versatile, lighter, better on yards, will grub and remove stumps, and more. Yard appears fairly flat so this would be a great TLB learning experience for you. Most are 3-point hitch-able too.