你好.不可以.
going to beijing --------往往强调现在还在路上.

The boy that will go to Beijing is my son==The boy to go to Beijing is my son -------这强调将来要发生.
The boy that went to Beijing is my son. 这是对的,但不可以改写成：The boy going to Beijing is my son,因为这强调眼下正在路上.