We just returned from Vegas.
Sooo much to do, it really depends on interest.
We try to hit a show each visit and saw Elton John last week. It was amazing-we've seen Celine Dion and the Rascal Flatts residency in the past.
Hotel touring can take all 3 days, each property is unique. We visited the Venetian and loved it.
Food is all over the spectrum, from fast food to expensive steak dinners. Check Groupon for some decent offers. We had Fellini's at the Stratosphere for a fancier dinner, probably the best steak I've ever eaten.
As for shopping, each hotel has it's own shopping "mall". Many are expensive and well out of the price range for "normal" folks. The Fashion Show mall is just like any other US mall, but is on the strip. I've had success at both the north and south outlets. The Venetian and Caesar's both have large malls inside for window shopping. There is a promenade near the Linq and the High Roller with some shops.
The Fremont experience downtown is worth a visit. We went on a Monday night and it wasn't bad. If you are ultra conservative though, you may find things you would not want a 13 year old to see, both on the strip an at Fremont. It's not fully naked folks strolling around at random though, just "interesting" outfits.
If you are not wanting to drive, take Uber/Lyft. It was around $7 for each ride from where we stayed (Trump International) to anywhere on the strip. Trump is very close to Circus Circus.
If you do venture out with the car, head to the Hoover Dam/Boulder City, the Valley of Fire, and/or Red Rock Canyon. All 3 are worth the drive and have amazing scenery.
Enjoy your stay, we've already booked a return trip for November.