What sorts of plants, trees, shrubs like clay-based soil (i.e., poor drainage), and lots of sun?
There are many plants that will grow in clay soils. Prepare the site by adding organic materials like compost or aged manure (do this when the soil is dry to prevent soil compaction). After the planting site is prepared, you should do a soil test to determine if you are deficient in any nutrients. This will also give the land a little time to settle before planting.
In general, you should select the trees first since they use the most space, and then work down in size with under plantings. Red maple, alder, hackberry, larch, sweet gum, sycamore, willow, and pin oak are a few tree possibilities. Shrubs like citrus, cotoneaster, sweet shrub, forsythia, and yews will also grow in clay. Perennials to plant could include astilibe, daylily, hosta, aruncus, and phormium. I suggest you investigate what has been successfully planted nearby to get other ideas. Most of these plants enjoy full sun.
Your local nursery should carry plants for your situation if the clay is widespread. In addition, the local cooperative extension service may have prepared a list of recommended plants for your area and for clay situations. They can also do soil tests or can let you know where to send the sample for testing. The small fee that is charged is well worth the investment compared to the costs of the landscaping.