I've been to vegas a bunch of times, although mostly for work....
One thing I'd DEFINITELY do is check out the Hoover Dam. It's not that far away, and it's amazing to see it in person... One time my family did a river trip down the river that started at the hoover dam, not sure if you're into that kind of stuff but it was cool.
Here's a place where you can drive an exotic car on a race track, I really want to do this next time:
http://www.exoticsracing.com/Exotic-Car ... as_6_1.htm
Go see all the free stuff, like the fountains at the Bellagio, the tigers at the mirage, etc.. I think unfortunately they stopped doing the ship wreck at treasure island... Also the canal in the Venetian is pretty cool as well. IF you want a lot of shopping, caesars palace has about every over-priced shop known to man (at the forum shops)..
I really enjoyed going to Benihana at the LVH, probably one of my more favorite places to eat (and really not that expensive).
I never have done the aquarium at Mandalay bay, that sounds really cool.
If you want free drinks, go to the penny slots, put in a dollar, and keep pressing "bet 1".. Eventually they'll bring you something, LOL! I'm not much of a gambler.. Be careful sometimes about the beer specials, one time they had $1 draft bud light, and I asked for a bud light, they gave me a bottle and charged me $6!!!!!