We are a mixed skiing and non-skiing family, and this is my resort of choice for a winter ski vacation, because of the mix of excellent skiing and many other non-skiing activities readily available. We started coming here many years ago, and just keep coming back each year.
The resort has it all, from the most gentle and wide beginners slopes, tons of intermediate terrain of all levels of challenge, to the steep, narrow chutes Motts Canyon, where even the super experts hesitate to tread plus a huge half-pipe for snowboarders. There is an excellent ski school for all levels of skiers, I usually take a lesson to brush up and try to improve a little. They have separate classes for the kiddies, too (see Heavenly Rockets in Family Fun in Tahoe Snow).
The two towns at the base, South Lake Tahoe and Stateline have everything a family could ask for in the way of amenities to make it a memorable vacation, shopping, movies, gambling, live entertainment, restaurants, sight seeing, plus a myriad of non-skiing outdoor activities.
Once on the mountain, you can ski from Nevada to California and back again all day, without coming back down to endure the crowds at the base. You can ski for nearly 6 miles from the top to the base in California, with a mix of black diamond to pretty flat terrain.
There are five restaurants on the hill for lunch, so just stay there and avoid the base crowds.
The views are indescribable, the most spectacular I have seen at any ski resort. From the California side you get a birds eye view of the entire Lake Tahoe and peaks surrounding the lake. From the Nevada side there are the expansive ranch lands of the Carson Valley and a pilots view of the city of Carson. Be sure to take your camera.
Although I prefer Heavenly as my base, no trip to Tahoe would be complete without at least one day trip to another of the major resorts in the area, Alpine Meadows, Kirkwood, Northstar, or Squaw Valley. They are all less than 90 minutes away in decent weather.
No first time trip would be complete without a visit to Squaw Valley, the only rival in size to Heavenly and the site of the 1960 Winter Olympics. If smaller is better for you, there are over 20 smaller downhill and cross-country ski areas around the lake, all of them with some excellent skiing.
The only cautionary statement I would make about Heavenly Valley is that the early season snow is less dependable there than some of the other resorts, so December can be a little iffy. I have spent a few dry vacations there, but side trips to Carson City and Virginia City, a dinner cruise on the lake, the shows and gambling at Stateline still made the trip worthwhile.