I live in the Bay area, so I love it here. One week, so many things to do, so little time. If you are first-timers, of course San Francisco is not to be missed. You can see most things in a day if you have a car, or maybe you can get the Red bus tours that drops you off & pick you up at certain sites.
I like both Lake Tahoe & Yosemite and I visit both every year, but staying in either will be a bit pricey. I'll just list the info I can think of and let you decide for yourself.
Lake Tahoe:
Things to do/see: Lake Tahoe - from the ground or up the mountains. We usally stay at South Shore (look for AirBnB), which is also near Heavenly Resort. Mustachian activities: hiking, biking, swimming at the lake (it's cold though even during summer), walking at the beach, going around Heavenly Village. Non-Mustachian activities: Riding the gondola up Heavenly and see an awesome view of the lake & surrounding areas; Brunch cruise around the lake. Neutral: kayaking, stand-up paddle (free if you have equipment/otherwise rent or sign up for an activity). Eat out or cook in as you please. Safeway/Raleys/other grocery stores abound.
Yosemite:
Sit/stand anywhere in Yosemite and you will be in awe. Activities are all nature-related - sightseeing, hiking, biking, learning about Yosemite, camping. There is an entrance to entering Yosemite Natl Park - $20/vehicle, good for 7 days. If you have a senior citizen with you, you can get a $10 lifetime pass for all National Parks! Hurray!! Lots of different sites to see, depending on your fitness. Most of them are driveable or you can ride the free bus that goes to most sites. There are some ranger-led hikes as well. For detailed info, you can download the Yosemite Natl Park app on your phone! or just check their website. The only "con" I will say about Yosemite is that usually the nearest places to stay is about an hour to park entrance. Once you enter the park, it will take you half an hour to get to the Valley where most sites are. If you choose to go to Glacier Point which is another beautiful site, it's an hour from the valley (though only abt 16 miles). I've once stayed inside the park as well, but that meant that we were near the sites on one side of the park, and an hour on other sites as well. So staying inside the park doesn't offer that much advantage, in my opinion. Much cheaper to stay in the surrounding areas.
Ok just shoot if you have more questions....