I wouldn't waste your time with two days at Heavenly. Heavenly sucks. You should go once, just to take pretty pictures, but you'll get bored pretty quick. Take the ride up to Homewood...it's small, but incredibly beautiful, quiet, and they have some awesome glades and the 55 (degree) bowl. Or try the chutes at Mt. Rose. But Heavenly...meh. Tourist mania.
I tend to agree with the above quote, If you're set on staying at Heavenly. I would do one day on the California side, then the other on the Nevada side. Just because it sucks trying to go from one to the other, especially for boarding. This mountain is made for skiers, too many flat/uphill traverses. I recal the Nevada has a couple of double black runs, Mott's & Killibrew Canyon. It's super steep! I could also tell you about the "Fire break" run, it'll take you all from the top, down to the casinos. Totally out of bounds, but fun when there's lots of fresh snow! Just don't get caught! I see you're going to Sierra for the day, glad to see you're going on a week day! Weekends are nuts there. Kirkwood should be fine for Fri & Sat, since its really in a remote location! Tucked away all by it self. Can't say that for Sierra! Since, it's first resort heading up the mountainl from the valley & Bay area. lines are very long on the weekends. Homewood on the other hand is never crowded, its off the beaten path. That is why I love this place. It's on the west shore of Lake Tahoe, storm clouds just hover over it and dump big! I think you have great itenary, looks like you'll be doing a lot of riding for 7 days! Save your legs/energy for Kirkwood!