We are on one day layover (2 adults, 2 children aged 13 and 14) in Beijing.

And would like to travel Qianmen > Chongwenmen > Beijingqiao, then walk Gie Jie to Dongzhimen and get airport train to Terminal 3. Could you please advise how much we should put on our Yikatong Cards? We'll buy these at Qianmen on 14th October.