I've gone to Vegas numerous times with kids and as a kid. I think there's a lot to do in Vegas, no matter what the age of your kids. There is a guidebook out there called Vegas with kids. You will see kids all over.
When we went to DL last time, we flew in and out of Vegas because the flight and car combo was about $800 cheaper than flying in and out of LA. On the way out, we drove through town and on the way back we went and did some visiting, and my kids, ages 4, 9, and 11 at the time begged to go back again and "just come here" (ie. Las Vegas.)
ESPN Zone is loads of fun for bigger kids. Each time we've gone to see the Freemont experience downtown there've been a lot of kids. Bellagio, always see kids. Honestly, I think there's lots to do.
You could take a Hoover Dam tour, a helicopter tour, or a show if you wanted to spend money.
You could go to see the tigers, Bellagio fountains, Freemont experience, play in the pool, and just walk up and down the strip with all the lights, for free.
For somewhere in between, you could go to Circus Circus, Excaliber, get funny pictures taken (like dressed up like medieval figures at Excaliber), see the lazer light show at Ceasars, see art exhibit at Bellagio, go in the gondolas, go to a 3D movie, drive out and see hoover dam, go to the outlet malls...the list goes on.
And, every fun type restaurant is available here....Hard Rock, Nascar cafe, harley davidson cafe, planet hollywood, rainforest cafe, house of blues, the list goes on.
I'd go for sure with the kids again, particularly if it's a couple to three days added on to your trip.