Personally, I don't think there's anything wrong with using silica-based sand, but make sure you wash it VERY well to eliminate the dust. The main problem with play sand or other quartz-based substrates is that they have a lot of zinc, mica, etc in it which break down very quickly in saltwater and will cause problems. Instead of using play sand or something similar, go to a pool supply place and get pool filter sand, which is bright white and generally free of the extra "contaminants" found in construction or play sand.
EDIT: Also, it's cheap! Probably less than 1/2 the price of aragonite sand. A happy medium between the problems caused by cheap play sand and the more expensive aragonite based substrate. As another option between pool filter sand and aragonite, you could look into dolomite sand, which is calcium carbonate like aragonite but comes from a different source (mined instead of taken from the ocean) so there's more "contaminant" minerals in it.