I agree Vegas is geared towards adults and the family friendly stuff has been gradually getting removed/replaced BUT I also think if it was to appease 3 other adults you can DEFINITELY find a way to kill a day or two with your kids.
Pick a hotel with a good pool set up for families - MGM hotel has a lazy river, M Bay has an artificial beach for example.
There's the rollercoaster at New York new York, zip lining and the lights at Fremont Street, gondola ride at the venetian, high roller big wheel at the Linq, Bellagio fountains, Eiffel tower viewing deck at Paris, madam Tussauds.
Then obviously you won't be going out clubbing but there's loads of family friendly options - or you could go to tournament of the kings etc.
You'll love it and your hubby can get a taster of what to expect for his 50th trip