Looking for things to do around San Francisco airport

You don't say how many hours you have to spend.
I would return the rental car and hope on BART and go into SFO. You can wander
around downtown, have a meal - there are several good places around Market St.
Then hop BART back to SFO for your flight.

We will have 2-3 hours before we need ti check in. I use a wheelchair, so it will be easier if we keep the car. We are going down for a wedding in Mill Valley on Saturday.

For lunch I would suggest you go to downtown Burlingame. It’s quite close to the airport.

Here are some suggestions;
1. Crepevine has both sweet and savory crepes. Always seems to be busy at lunch and weekends.
2. Il Fornaio.

3. Stacks for great pancakes, omelettes but they serve sandwiches too. Closes at 2:30
4. Max’s for NY deli style food.

Also Copenhagen bakery for pastry.

Lunch in Burlingame is a good idea if you want to keep the car due to the wheelchair. Traffic is horrendous so I would want to be nearby.

There is a vast array of choices for restaurants that are within a 10-15 minute drive (less than 5 miles) from the airport, in San Bruno, Burlingame and San Mateo, even Foster City. Downtown San Mateo and downtown Burlingame probably have the best choices, but if they don't have parking lots, it may take a few minutes to find a parking spot.

Everyone has their favorites, a lot depends on what kind of food you want. I usually go for Mexican food since I can't get it at home. Chili's on El Camino in San Bruno was good a year ago (last time I was there), even though it's a chain, and they have a parking lot.

May I suggest 3 rd st San Mateo for a nice reasonable asian fusion meal. Pacific catch.
Or south San Francisco city at the Basque cultural center for a big hearty meal.
Very close to SFO. Parking no problem.
If u decide to sight see then go to Pacifica drive the coast line to Half moon bay then overr hiway 84 to airport. Do not try this during commute hrs .

That's a great idea - after morning rush hour, cross the Golden Gate Bridge, then stay on 19th Ave which runs into 280, exit to Hwy 1 to Half Moon Bay, excellent scenic drive. Continuing on 1 to 84 and then back up 280 is a long loop, but nice if you have the time. If not, just take 280 from Half Moon Bay toward wherever you're going for lunch near the airport.

Here is a good government resource for avoiding morning, midday and afternoon rush hour traffic or at least see where it is bad:
http://quickmap.dot.ca.gov/
On the QuickMap tab "zoom" to San Francisco.

If you decide to go to Half Moon Bay, we had a great meal at Moon Pasta. We drove up from Half Moon Bay to the airport.
Even at 7:00 am, the traffic was pretty heavy near the airport.
Since you have a wheelchair, give yourself at least 45 mins just to return the rental. The return is ground level. The shuttle is upstairs. There are elevators. The ride is about 10-15 mins plus factor in maybe 5 mins wait. Then it's down to the airport level.

Thank you all for your great suggestions!