My guess is that if game managers were seriously concerned about calf survival they would dictate no shooting mother with young. That being said - the calves would be the most vulnerable, especially without mom. Yet that may not be entirely true either. After rut the males are often the most vulnerable - exhausted chasing and fighting for the ladies. How big is a calf moose? A cow and calf ran into me the other day - and the calf was huge - though probably last year's, not this. If I could drive to the kill spot - maybe the cow. If I had to pack the kill over hills, across ravines, and through jungles to get to my rig ... BANG! (drop the calf).
I don't know how mom would react to you walking up to her dead offspring. If the calf was indeed dead - I suspect she would stand there - and eventually move off. They protect life - but also know death. Tomorrow she'd probably forget she even had a calf - she'd dry up - and start looking for bulls.
My 2 cents.