Rhododendrons come in dwarf sizes. They prefer being in the shade. They have pretty lavender and pink blossoms in the spring.
Most azaleas are dwarf sized. They thrive in the shade with bright pink, red, lavender and white blooms in the spring.
According to Harold E. Greer in "Greer's Guide to Available Rhododendrons," all azaleas are rhododendrons.
Cheryl S. Smith lists many dog friendly small shurbs that grow in the shade in her book "Dog Friendly Gardens." Physocarpus comes in a dwarf size with pretty fall colors and peeling bark. She notes that dwarf hydrangeas that bloom on new wood are a good choice. . Viburnum come in dwarf sizes that do well in the shade.
Daphne comes in small sizes. It is an easy care shrub that needs little water that thrives in the shade. The Carol Mackie version has gold edged leaves with white blooms.