I wouldn't worry about being stung... I've had rays for years and never been stung. But none that I know of, even in the wild, are deadly. Bluespots and yellows live in warmer waters. Bluespots are very delicate and hard to keep alive for a long time in a tank. Yellows are very hardy, inexpensive and relatively easy to find. In addition, they are one of the smaller species of aquarium stingray. You could also consider a bullseye ray if you could find one.
They need a deep enough substrate to be able to bury themselves. 2 inches is a good depth.