http://www.dakota-durango.com/forum/showthread.php?t=4487
^^ Mopars at the Strip contact thread, it's in the Events section.
I would highly recommend coming out to MATS even if you aren't 21, you will still have a helluva good time at the event itself, and as long as you stay away from the gambling at the hotel I think you should be able to come in and hang out to watch Kenny Wayne Shepherd play. I wouldn't be surprised if a number of people at the event are just planning to hang around at night, and there will probably be other <21 people too. There's still plenty of stuff to do in Las Vegas if you're under 21 - cruise the strip, see the casino sights (the roller coasters, bellagio fountain, mirage fountain, TI sirens show, etc), there's non-alcoholic 18+ strip clubs, etc. You can go into any casino, but you can't loiter in the gambling areas or lounges (doesn't leave much, but some places are worth just walking through).