Well, we went for a few hours with my kids before and after we drove out. They told me that "next time" they wanted to get to spend more time in Vegas.
We did Bellagio fountains, drove up and down the strip, did the downtown Freemont exhibit. They were twirling around taking it all in. They wanted to see "more more more". They loved all the lights and excitement. They wanted to see and do so much.
And, honestly, my kids would have fun in Vegas if all we had was a "neat pool", their number one requirement.
With your DD being 13 and DS 7, I'd be surprised if they'd be truly bored, as long as you planned family time to go and do things. When I was a teen, I went to Vegas with my family a few times, and I have to admit I was bored silly, but the adults in my party were more focused on gambling than they were at keeping me entertained. When they did take me out and about, I did find a bunch of things to interest me. Plus, there's now tons more stuff to see and do, in my opinion.