From what i know, there is another Clamp School Detectives wiki. One that was created before yours. The lack of traffic may be because the other one is older and more developed? Either way, I can help with organization and proof reading at most. But I wouldn't be able to contribute much in terms of series specific information.
What about xxxHolic (one of Clamp's works)? Sakura, Syaoran and Clow Reed was mentioned by Yuuko. Yuuko know Clow Reed very well, xxxHolic is connected to Cardcaptor Sakura, Tokyo Babylon and Tsubasa: Reservoir Chronicle
I have not read any of those other than Cardcaptor Sakura. The only series of CLAMP's work that I have read are Cardcaptor Sakura and Magic Knight Rayearth and Clover. I am aware that many of CLAMP's series are interconnected.