The mother's funeral as a foreshadowing of the death of Russia
The little boy has, as yet, no comprehension of what he has lost.
That's an interesting interpretation.
I had taken it as a personal characteristic of Zhivago, that his mother's death had made him more introverted and sensitive, which is what led to him being such a great poet, but I like your external interpretation as well. Certainly the fall of Russia had the same effect on him, throwing his life into disarray and ultimately forcing him to find a new home. It's a good foreshadowing as you say.