I don't think that meditation is normally taught together (as a part of) taijiquan. In Beijing, perhaps you can go to the Baiyunguan and talk to the Daoist priests in there. Another option would be to go directly to qigong circles (perhaps by meeting teachers by taking medical qigong courses, etc.).
As for taijiquan, there is lots of Beijing - but Cui Yishi's line is interesting, besides Cui Zhongsan, Zhang Yongtao is another grandson, and there is a whole organization of Cui's line teaching actually (http://www.taiji.wang/wap/?14631.html
). Cui was one of Yang Chengfu's earlier disciples, and he may have had a more "complete" taiji system than later disciples. If you want to do Chen style instead, there is always Chen Yu, too. (This hunyuan taiji site (http://www.hunyuantaiji.com.cn/
) lists Chen Xiang among its instructors.)