I'd be careful not to add the inverts too soon. Some of these bags of live sand sit on store shelves for months before they're sold. There is often die off from time, temp fluctuations, and other factors in shipping and shelf life. This can show an ammonia level for a short time when first put into the tank. I always make sure to poor off any liquid that might be in the bag before putting it into my tank. This helps to decrease that risk.
If this is a new tank, then it will still also need to cycle, and inverts will be very sensitive to that, more so than most fish. The live rock and sand together for the first 4 wks should be enough to get you stable, and then I would start with 1 small fish, wait 2 weeks, and then begin stocking maintenance crew.
Hope this helped.