Some more ideas, in addition to the many good ones that have been mentioned here:
- Definitely go to Edgewood as mentioned above to dine and/or walk along the beach there - I think it's the most spectacular property open to the public on the lake. Brooks bar outside is a fantastic setting (was there last night again). There is fancier dining in the beautiful setting in the main dining room at Edgewood, or another one both indoors and outdoors at the Edgewood bistro in their newer adjacent building.
- South Lake is becoming a craft brew haven, with lots of nice brewpubs with indoor and outdoor space. Two newer ones near Heavenly Villlage are Flatstick right across from the Timber Lodge, a huge space with indoor/outdoor dining/drinking and an indoor 10 hole miniature golf course; and Third Man down by Ski Run Blvd. with a really nice interior, good pub food (fresh warm pretzels with cheese dip, mmm) and good beer selection. Tahoe AleWorx at the Y is a great outdoor space flanked by the brew pub on one side, wine/cocktail bar on the other side, a new food stand outside to go with their indoor kitchen, and large outdoor space in the pines with fire pits and a live music stand. Some other breweries/brew pubs - South Lake brewing (my favorite of the beers), Sidelis, Cold Water, South of North, Stateline, the Hangar, the Brewery at Lake Tahoe, and a second AleWorx in the Casino row.
-Visit Sand Harbor on the east side, rent new glass bottom kayaks or hang out on the beach. Nevada beach and Round Hill Pines beach are also nice, and you can rent bikes and ride on miles of paved bike trails in that area around Stateline too.
-Visit Thunderbird estate, if it's reopened for tours by then. Down along the south side near Camp Richardson are a few other old preserved mansions for public tours too.
-Drive back to the end of Fallen Leaf lake - boat rentals, hiking, and outdoor patio for sandwiches and lunch there too.
-Drive to Incline Village - Try Alibi Ale public house, the restaurant Bite, the Eagle lounge of the Hyatt on the lake, or Big Water Grille.
- Stop at Logan Shores vista overlook north of Cave Rock tunnel, hike down to lakeshore trail if you don't mind short steep paths. There are several other good vista points on the east side that have nice views and trails down to lake access.
- Check in at forest service run Info center at Heavenly village to discuss possible hikes and other tours and get maps if desired. There are endless options around the lake, and various sources of info on websites, trail maps, and guidebooks. A couple other areas to check out on day trips are Spooner Lake on the east side and Tahoe Meadows near Mt. Rose on the north, with trails in both areas, and access to the Tahoe Rim trail for lake views after climbing a bit.
- Dine at Riva grill or Artemis at the end of Ski Run Blvd. overlooking the lake on outside patios.
- Check out various other beaches via this website:
https://www.tahoepublicbeaches.org/
This is still just scratching the surface, there is way more to do on all sides of the lake. Driving around the whole lake in a day is worthwhile, and you can see some of the options for additional day trips by doing that. Make time for a stop in downtown Truckee and maybe Tahoe City too.