It tugs at my heartstrings, too, but "officially" elk calves are weaned by then, regardless of the fact that I have found milk in the udders while dressing elk.
I have found milk in a doe deer I killed in November, so I'm not sure when the cut off is for ANY nursing.
I have had pretty good luck with getting shots at the yearlings, because they are a little dumber...
Now, for the cold hearted perspective. There is a mountain lion somewhere on every mountain I'm hunting. Tonight, she WILL kill a calf elk to feed her half grown kittens. It might as well by the one you orphaned as any other. Calves ALWAYS experience the highest mortality rates, period.
Or, you could shoot the calf if it's big enough.