My trip was supposed to be only to Los Angeles, instead I was surprised with a little get away to the Sin City, and I loved it. It has been a while since I've been thinking about going to Vegas, and it is a great place to spent a long weekend. There are many things to do, and be prepared to walk a lot, and it is a good thing all the hotels in the Las Vegas strip (new Vegas) are connected by sky-walks, and parking (at the hotels) is free everywhere (or self parking as they call it).
Just make sure to check out the Old Vegas (downtown), or Freemont Street, this is where the original casinos started, and where the giant neons signs were located. Today the street has been covered by a giant projection screen, and this is where the locals go to gamble.
Another thing you should do while in Vegas, is to go see one of their famous shows, and there are many of them. Do not forget to check the discount box office for cheaper show tickets. I had the chance to see the Cirque du Soleil show "O", and what a treat that was. If you have an American Express, and you buy the ticket at the Bellagio box office you will get 25% discount.
Definitely I recommend this city for a long weekend, just not sure about bring the kids with you, maybe you will enjoy the city more without them.