Vegas Vacation

My family is going to Las Vegas in a couple of weeks. It's just my husband, me & our 2 year old daughter. We've never been there (unless you count sitting in a plane at the airport) and this will be our first family vacation with just the three of us. 

That being said, I'm posting to ask for your help. Have you been to Vegas? Is there anything that you recommend we do while there (we'll be driving up on a Monday and coming home on Thursday)? Is there anything you've done that was totally NOT worth the time/money? I'd love to know what you all think!

Thanks!