You live near the beach. You'd be better off using sand than DE. DE is useless when wet until it dries...that's if it doesnt wash away in a thunderstorm. Sand wont wash away and dries quickly, think beach. If you think DE is okay to eat...make sure you tell that to the doctor at your next ER visit.
This is the best article I have found for DE. http://www.richsoil.com/diatomaceous-earth.jsp I use it more for pest control in/around my coop then for the health of my birds but I use it in my house for myself (yep eat it) and my dogs (flea control). ONLY GET FOOD GRADE no matter what.
I'll stick to the coop reason. I live in Pensacola, FL in the city limits but here is the kicker I have a wooded lot. That means bugs and lots of them. I went into my coop back during the summer in middle of the night (i forget why) and was shocked to see how invested the coop was. No wonder my girls didn't wanna go to bed at night! So after I clean the coop, I "powder" it down. This is usually in the early morning before work so the dust has a chance to settle before the girls go in for laying.
I tried powdering them with it but didn't see a need as, Knock on wood, mites are one of the few bugs I don't have.
DE is cheap and 100% natural! so I guess it all depends on what your trying to accomplish with it for it to work. Just remember it won't kill anything squishy! LOL but it will do the trick on some crunchy critters!