3-hour layover in Beijing

We are 6 elderly passengers. We have a 3-hour layover in BJ and 9- hour layover in Shanghai on a plane from Nagoya going to Manila. We are interested to go to BJ downtown during our 3-hour layover. With this tight timeframe is it possible to take a quick downtown tour on our own
without missing our flight? We plan to take the train from the airport and back. Please advise.