Our beach sand is the consistency of flour and so is the launch area behind the beach.
Sand would cause extra wear on all of your equipment including the wing. Just be careful not to stir up more sand than necessary by doing foot drags and such. As long as there aren’t iron particles in the sand it shouldn’t accumulate inside the motor. You could blow it out with compressed air occasionally if you are concerned be people launch on beaches all the time.
A few sprinkles of rain won’t hurt anything if the battery is disconnected. You should never fly in rain so your battery should never be connected during rain. But why would you ever expose your machine to the rain in the first place? It comes apart to fit in a car so there’s no reason to ever leave it in the rain.