There are a ton of things to do in Vegas. Here are a few things. Hope this helps a little:
Circus Circus free Circus acts throughout the day- also the Midway, tons of games.
The Atrium at the Bellagio and also the water show. This is a must.
The Canal shops and boat ride at the Venetian
The Fremont street experience. This is downtown.
M & M World
Coca-Cola World. Take the kids here, you can buy a sample tray for very little and taste different soda from around the world.
New York New York has a great Roller Coaster for the kids
Sahara also has a "Fast" Coaster and also the simulated Nascar
The Stratosphere has a bunch of things at the top. I guess it depends on how daring the kids are.
Tournament of the Kings dinner show at Excalibur
Lance Burton puts on a great show for the whole family
If you have time drive to Primm which is about 45 minutes south of Vegas. It has a Roller Coaster at Buffalo Bills that's pretty fun.
The Pirate show in Front of Treasure Island TI. Just a note, it has changed from what it use to be and is more adult oriented. Maybe for the adults. I think the kids may not like it. The 14 year olds will, lots of sexy ladies. ;-)
There are a few things-Hope that helps. Have a great time.