I think that's a great idea for a trip. We loved Tahoe and will be back again soon. We much, much preferred the North Side to the South Side. We stayed in an AirBnB so I can't comment on a resort, but I would highly recommend Tahoe City if you can find a place.
Things to do:
-Eat at Cafe Fiore. Aggie owned and very intimate setting for an anniversary dinner.
-Our favorite beach was Sand Harbor Beach. All of the beaches were nice but Sand Harbor had the best combo of sand, walking trails, and different scenic views all in one spot.
-Go take pictures at the lookouts over Emerald Bay. If you like hiking, I'd recommend Eagle Falls while you're there. Get there early or late because parking is an absolute nightmare.
-Take pictures from Eagle Rock. The hike isn't too bad and the views are awesome.
-Take the short drive to Truckee. Lots of shops, restaurants, walking trails, biking trails, and/or fishing available.
I have a whole list of things that were just ok and some we didn't enjoy at all, so if you want more feedback just throw out more ideas.