The sand will soon become coated with bacteria which will hold it down. You may get some sand shifting around at first, but it will settle down. I have most of my powerheads close to the surface and aimed so their flow collides with each other. This will give you the surface disturbance you need to facilitate gas exchange. You also want turbulence in the tank instead of laminar current. Remember, we're trying to simulate the wave action on a reef as closely as we can.
I don't recommend stirring the sand bed at all. The critters in the sandbed should keep it stirred enough. I have, and I hate to mention this because it may be confusing, read about some folks stirring their sandbed to stir up food for the corals. I don't do this and I would urge anyone to be very careful if they try it.
Life is not measured by the number of breaths we take, but by the moments that take our breath away.