That's going to be a challenge. My soil is silt and sand and drains very well. I have tried several tall fescue blends over the years and every one has struggled to thrive/survive once we get near the solstice, and the weeks beyond. I have many large trees surrounding my 'grass patch' so that greatly exacerbates the problem.
My advice is to do what I did and minimize the grass area as much as possible- increase mulch areas, add raised beds, build a fire-pit with a large surround and add more plants. I still want to go total hardscape, but stone and rock isn't cheap.