Is the pronunciation of a heteronym in a given name indeterminable unless we ask the person personally? There are tones of heteronyms in Chinese and when a heteronym is a given name, or a part of a given name, is asking the person (or his friends, relatives, etc.) the only way to find the pronunciation?

For example, do we know for sure if 劉禪 should be pronunciated as ㄕㄢˋor ㄔㄢˊ unless we ask 劉禪 himself?
We don't actually know how to pronounce it. 
Usually based on the meaning of the word on the bright side. But, in this case, both the meanings of  ㄕㄢˋand ㄔㄢˊare very good. So, how to pronounce it is up to you.