I cannot help you specifically based on the information provided, but perhaps, if you have not done so already, take a look at the history of the Chinese in Indonesia. It will perhaps provide a foundation on how your ancestors may have fit in its history, and maybe even provide a key link in search of your genealogical past. Check out this website: http://www.tsinoy.com/article_item.php?articleid=662
Afterwards you may want to start looking into possible family associations in Indonesia such as for the Tan family clan. Family clan associations may have information on your ancestors. Do you know where in China your ancestors were from?