You've done a good job and make some good suggestions.  I would lean towards the Viburnum or the Serviceberry as they are both native trees for the Chesapeake Bay watershed region. Other common small native trees are various types of dogwood and redbud. The Extension Service strongly recommends plants native to this area as they are adapted to local soils and climate conditions and, therefore, often require less care.  In addition, native trees benefit the local ecology. Following is a link from the Md. Department of Natural Resources of recommended trees, most if not all of which are native.

https://dnr.maryland.gov/forests/pages/marylandersplanttrees/recommended-tree-list.aspx

You also should consider if the planting area is mostly sunny or mostly shady, wet or dry soil.

Lastly, following is a link from the Extension Service on how to plant a tree which may also be helpful.

https://extension.umd.edu/resource/planting-tree-or-shrub

Debbie

I don't want to be too discouraging, but a container grown tree is not likely to grow 15-20 feet and provide shade.  That is why I didn't think you were talking about planting the tree in a planter.  Dwarf varieties of trees and slow growing trees may do well in a planter if they are kept moist and fertilized, but I'm not aware of a native tree that is well suited to growing in a planter.  Dwarf Alberta Spruce, Japanese Maples, and Dwarf Crepe Myrtles may do well in a 5-gallon container, but will most likely not get larger that 6-8 feet.

Debbie

Many grasses will take a hot, sunny and dry environment which you describe.

Switchgrass (Panicum Virgatum) will grow 4-6 feet tall.

Debbie