Hello! I live in Southern California and frequent Las Vegas often. I have not heard of that web site before. I would recommend being cautious in using web sites or services like that in Las Vegas. Sometimes you can find a great company, but often you'll not get what you paid for. I would ask any friends or bridesmaids if they have any connections. Also, check in with the concierge at the MGM Grand or with the shows you are interested in watching. They may have bachelorette packages available. Groupon or Living Social often have deals associated with Las Vegas shows and activities. Airlines will also have airfare specials to Las Vegas. I have noticed more airlines offering direct service to Las Vegas from the South, Midwest, and East Coast.
Since you will be there in August, pool parties at the MGM or other hotels can be a fun day time activity. It still will be really warm at night so you can walk the main part of the Las Vegas Strip to enjoy all the hotels, water shows, bars, etc. And in all honesty, bachelorette groups receive a great deal of attention and perks in Las Vegas so you and your girls should have a great time! Good luck and enjoy Las Vegas!