Can I use a kohler a 1/2 thermostatic valve (k-2972-ks-na) with 3 body sprays (K- 8509-CP) The valve states that it can handle 10.9 gpm, each body spray needs 2.5 gpm and the shower needs 2 GPM. Can I trust it?

You are definitely pushing the limits, but according to the specifications you should "just" be OK here. If you want absolutes you'll need to contact kohler company directly:

Phone: 1-800-4KOHLER (1-800-456-4537)
Hours: 8:00 AM - 5:00 PM (Central Time) Monday through Friday

I believe you'll also need to pipe the multi. body sprays in a special pressure balanced loop...see image. Again, however, the instructions that come with the body sprays will trump any of my advice so be sure to read them as there are a few different pressure balancing loops that are being used out here nowadays! If you do not pipe the body sprays as needed you will definitely have a less than pleasing shower experience, so don't look for any shortcuts here, OK?

Good luck!

Mark