You may try senior discount in that case - many hotels offer senior discounts on room rate. Some additional notes about SF hotels:
1. Some hotels are close or next to cable cars and can be quite noisy.
2. SF Hotel rooms are typically smaller. You obviously will need at least 2 beds for 3 persons. Keep in mind in many SF hotels 2 beds could be 2 full size beds (smaller than Queen).

I am a little hesitant about recommending any particular hotel to you because we have different needs and what works for a solo traveller may not work for you (3 adults), and even more so in an expensive city like SF. That said, here are some ideas:
1. Close to Chinatown: the Hyatt on Stockton Street (there are 3 Hyatts in SF city) and the Hilton across from Chinatown (there are 3 Hiltons in SF). I have stayed at the Hyatt but not at the Chinatown Hilton, which used to be a Holiday Inn (bought and renovated by Hilton)
2. Hotels in the Fisherman's Wharf: I have stayed at Hyatt, Hilton, and Marriott in this area. They are all kinda old and need some renovation but still decent hotels. Fisherman's Wharf is touristy. Holiday Inn and Courtyard by Marriott are in the area as well.
3. Union Square: close to shopping, cable car, the theatre district and downtown core and a longer walk to Chinatown. Hilton, Westin, Hotel Monaco are the 3 I frequent, depending on the price. Avoid the area west of Union Square, which is Tenderloin, a high crime area.
4. Financial District/Mission: Marriott, the new InterContinental, Westin, etc all have their property here. This area is a little farther from Chinatown and the scenic areas but close to the Stadium and train station. Mission district traditionally has a bad rap with crime but has improved in the last decade.
5. Nob Hill: Some very nice hotels here - Fairmont, InterContinental and Stanford Renaissance (by Marriott) are almost right next to each other. Do not recommend this area for older people due to the very steep hills.
6. Japantown: Hotel Kabuki is nice and sometimes well priced. The parking garage next to it charges $15, which is a bargain for hotel parking in SF. Advantage of this area is its vicinity to all the Japanese food within walking, but it is outside the downtown core. Keep in mind, the core SF is fairly small and you can easily get around by bus.
7. Civic Center area: never stayed in this area, high crime area and not recommended.

If you are driving, you may be able find cheaper or free street parking (less likely in the downtown core). Note the following:
1. Pay attention to street cleaning day - you will be ticketed or towed if you park at a wrong spot.
2. Parking on a hill: turn your wheels away from the curb when parking uphill (front pointing uphill) and turn your wheels toward the curb when parking downhitll.
3. Remove everything out of your car for overnight. As a minimum, when parked please do NOT leave anything visible in the car (including your tourist map or anything that can give you away as a tourist)
4. If you take the bus or MUNI, watch your purse/wallet. Pocket pickers frequent the bus, and even more so with the current economy. The Chinatown Stockton line is notorious for this.

Hope this helps.

Happy Travel!