It's really tough to say SmashBurger has the "best burgers" in town, as I think The Palm (Caesar's) does, though that is really subjective...but it's easy to say it has great burgers, great sides, fine service and a pleasant atmosphere. I've been there at least a half dozen times. The Classic is my favorite, though I've tried others; and the Smash Fries are just grand.
For a quick lunch or dinner, at very reasonable prices, in Summerlin, give it a try -- My guess is you'll like it.
For the record, the "Good for kids?" survey question is one to which I'll always respond "No," as I'm so tired of having them run about and yell where I go -- Take 'em to Chucky Cheese.