There are at least a dozen companies that offer trips to the Grand Canyon from LV, either by bus or plane, so take your pick. I can't recommend a specific company myself, but there are plenty of people here that have taken tours with one or the other, and all major guidebooks to the city have lists of such recommendations as well. I might suggest you get a guidebook. There are a lot of things to do in LV besides gamble and drink.

The Grand Canyon is best viewed at sunrise or sunset when the rock is most dramatic in the light.

The bus tour will not provide that.

It's about 4 hours by car. If you rent a car, stay overnight to get the full impact.

If we end up with a rental car, we may just do that and stay overnight, but I just want to weigh my options. I know there's plenty to see and do besides gamble and drink, that's why I came here for suggestions (as I always do) before going out to buy a guidebook.

Speaking of guidebooks, buy Fodor's Arizona & the Grand Canyon 2012. I'm quoted on page 483 under "Word of Mouth".
Setting your own pace with a rental car is always better than a bus tour and much cheaper than doing anything that involves flying.

My brother and I took a plane tour from LV to GC with Look Tours. Pick-up and drop-off at our hotel. We took the 6AM tour which I believe was back in Vegas around 2PM. Less than an hour flight with views of Hoover Dam and Lake Mead. Then hopped on a tour bus at GCY airport. There were a few stops at the best South Rim viewpoints. Definitely enjoyed it.

We took an airplane tour to the Grand Canyon for the day years ago. Tour Bus, which was part of the package, picked us up at the Grand Canyon area when we landed and took us around.
Loved looking down on the Canyon as we flew over it.
I think it was called Southeast. We did this 8 or so years ago.

One day drove to Zion NP for 2 nights from Vegas. Beautiful park.
We also drove to Bryce Canyon on our 2 night Zion NP trip.

Another time we drove in March just for the day to Zion and hiked a little.

We do not drink and gamble either, but Vegas is so much fun just walking through the hotels. You can go see Terry Fator, Blue Man, "O"show, and a few other family friendly shows.

We love driving to Henderson, NV and eating. It is about a 20 minutes drive.

Vegas is one place that it make sense to rent a car if you don't gamble. Cars are comparatively inexpensive to rent and would probably be less than a tour for two. There are several other places nearby to visit in a day, like Valley of Fire, Hoover Dam, Red Rock Canyon, and Death Valley.