Of the properties you mention, the Polo Towers should be the only property you're looking at if it's your first time in Vegas. It's right there on the strip with easy access to the Deuce bus.
Since you've never been, I can understand your concern about family friendliness. Vegas is most definitely family friendly, just play it smart. There's so much to do for you to do with your 15 yr old together to make the trip worthwhile.
Some ideas:
Visit...
- the Bellagio Conservatory/ fountains
- Grand Canal Shops at Venetian
- Forum Shops Caesars
- Area 15
- Paris Eiffel Tower observatory
- South Point casino
- Circus Circus Adventuredome
- Downtown Fremont Street
- NYNY roller coaster
- Excalibur Tournament of Kings
- Mandalay Bay Sharkreef
- Pinball Hall of Fame
- Definitely more but can't think of atm
Expect a lot of walking, but it's amazing seeing all the different properties inside and out. Casino spaces are usually identified by the carpet, so as long as you keep moving your 15 year old can walk through them, even alone.
If you go there knowing it's not
Disneyland, you'll appreciate it for its uniqueness.
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Pro tip if you don't have a car: purchase a residential day pass bus ticket on you phone or onboard one of the numbered buses for $5. It works on ALL buses including the Deuce and express routes. If you purchase your bus ticket from a machine or onboard the Deuce, they'll charge you $8 for a "Strip/All Access" pass which is a tourist trick.