Robin, I can offer a great tip for adding a new sandbed without any sandstorm.
First, since this is a new tank and you want to mix the salt right in the tank (no problem there), just add the ro/di water to the system.....AFTER you put the sand in the tank.
Cover the sandbed with a large plastic garbage bag cut to the rectangular shape of the tank. Put a pot on the garbage bag and pour the ro/di into the pot until the tank is filled.
Next, add the salt to your sump and it will circulate through the tank and everything will stabilize naturally.
Nice and easy, no sand all over your rock, no milky sandstorm to wait to settle......just crystal clear water.
Best of luck with your new setup. It's beautiful.
Russ