I’ve got an office in Vegas that is right off the Strip- I assure you that those guys are still there in hoards.
As to the OP. . . I just don’t think Vegas is a place for kids. Does that make me a threadshitter? I dunno, I guess I’m just perpetually baffled by the families I see, dragging miserable looking kids through casinos and down the Strip. Sure, there are some kids activities, but over all . .. it’s hot, it’s stinky, and there are drunk assholes everywhere.
It’ll definitely be hot and while there isn’t humidity, 115 degrees is the kind of hot that burns your lungs just to breath in. Your eyes are going to burn just to keep them open outside (not literally like, scorch, but I mean the physical sensation of INCREDIBLY HOT on your eyes/throat/chest). I wouldn’t count on being able or willing to walk around outside much at all- so take that into consideration when booking your hotel and find a place that has a tram system or that is interconnected with several other places. Or just rent a car- valet parking is free everywhere in Vegas (of course you need to give them a few dollars as a tip.
FWIW: the Mandalay has gone way down hill in the last few years and their prices really haven’t adjusted to reflect that. I guess they got bought out by MGM or something and ever since, it’s much. . .well, less kept up than before. I would suggest going and signing up for just about every hotel’s mailing list. Because I stay in hotels whenever I come to my office there, I’m on all the mailing lists and you wouldn’t believe some of the “BOOK IN THE NEXT 12 MINUTES AND GET 900% OFF**” deals I get in my email. I recently stayed at the Vdara for $65 a night on a week day (AMAZING hotel- I had a view of the Bellagio fountains) and then, the last trip, I stayed at Cosmopolitan for $85 a night (balcony room, 65th floor, one bedroom suite, over looking Bellagio fountains). Even sites like Kayak can’t touch the deals that get emailed to you by the resorts directly. Also: take into consideration that many of the places charge you a daily resort fee ($15-$20) PLUS you have to pay if you want in room internet (another $12-$20). Certain companies tout that they don’t have a resort fee- I want to say the City Center hotels don’t. . .as well as one other, but I can’t remember who (was it the Gold Coast hotels maybe?). Anywho, my point is to take that into consideration when factoring the cheap prices at somewhere like, say, Mandalay.
As far as things to do, we’d always take my friend’s kid to the Secret Garden at the Mirage-- it’s where they keep all of Siegfried and Roy’s animals. They also have a pretty neat dolphin habitat. I haven’t been there in a year or two, but the kid always really enjoyed it. Oh, I’ve heard the aquarium at Mandalay is not even remotely worth the money.
**NOT ACTUAL NUMBERS 
I am sitting in a Vegas Arby’s right now, getting ready to go to the airport. It is 100 ish at 11:30 am but it’s not crazy. Just stay inside.
Don’t bring your kid here. There is nothing for them to do, the other adults won’t appreciate it, and you will not have much fun. There is literally porn on the streets, a zillion drunk twenty-somethings, and your kid will hate the packed crowds on the strip.
Now, if you were to find a good off-Strip hotel, there are lots of beautiful natural parks and such nearby. Just stay away from the Strip with the kid - you’ll look like a fool.
ETA: we love the card flickers. I am the elected card collector, and we got about 4" worth this time. Free porn!
I frequent some Vegas boards, and we pretty much agree on one thing; the best thing to do in Vegas if you have kids is, get in your car and get on I-15 south until you reach Anaheim (there’s a Disney there as well as the one in Florida, and it’s not nearly as humid).
If you want to go somewhere with gambling that badly, have you considered Lake Tahoe? At least there’s a lake there for something to do during the day.
Then again, what do you expect to do with your child at night? Apparently, they do allow children in the Blue Man Group show, but do you want to pay that much for an extra ticket (apparently there are no discounts for kids, and anything other than a nosebleed ticket costs over $100)? You could always go to a movie, but that defeats the purpose of being in Vegas in the first place.
Also, I assume that only one of you at a time would gamble? A five-year-old in the gaming areas is out of the question, even if you’re just sitting at a slot/video poker machine.
Within our group of friends, we make it into a game, with ‘prizes’ for - who gets the most cards, who gets the most varied… and any other stupid category we can think of.
I third or fourth the idea that Vegas, specifically the strip, is not for kids. They abandoned the whole family vacation marketing ploy years ago.
We were there in January - yeah, Vegas is not for kids. Not only do you have the cards for prostitutes, but there are some lovely billboards - including one rather sleazy one on Fremont Street - for strip joints.
If you don’t want to do Disneyland - how about Monterey/San Francisco. Monterrey has an awesome aquarium that is a huge hit at that age, worth a full day. Alcatraz - if it isn’t too scary for him - rocks. Muir Woods is great. And you can ride a trolley.
Kids will want to see the cool things on the strip (Bellagio fountains, pirate show, NY, NY) but in August all the glass and traffic and pavement combined with the heat can raise the “official” temperature by 10-15 degrees.
If the kid sees something she wants to check out on the other side of the road, it can involve walking for blocks to find a rare crosswalk or overpass, then walking blocks back to get to your spot.
Well I’ve been here on Vegas for 4 days and I can safely say that your child will not be out of place. I must also mention however that my judgmental bitch hat is getting a hell of a workout, usually around midnight walking down the strip.
There is no shade in the pool areas except in the cabanas and at Mandalay those run $575/day and up, so plan on frequent trips between the beach and your room to cool off.