I just happened to think, can you get some shade cloth like they use in nurseries? I put some on and it really does dial down the direct sun. I think some places sell it by the foot. I got a prepackaged roll of it which was plenty for what I needed it for. Other than that you can put lawn chairs or anything they can get under or that can cast some shade.
Lowes sells it by the yard, it is located in the garden section.