Maybe not any more necessary, but at least less cruel? Animals raised to be killed and eaten - done and over with. Animals living years and years in cruel and inhumane conditions.
To clarify, I'm not vegan because I feel it is inherently wrong to eat animals. I do think it is wrong and cruel the way that animals are raised to be eaten and the way that animals are slaughtered in America. They live in inhumane filthy conditions, and die unnecessarily horrible deaths. It is definitely true that the suffering of the elephants lasts a longer time, so in that sense it is worse. But I am not sure that they are treated any more cruelly than animals on factory farms or massive slaughterhouses, they are just treated cruelly for a longer time.
If kids want to see elephants, why not take them to the zoo instead of the circus? It certainly isn't an ideal situation for the elephants living there, many of their natural behaviors are necessarily suppressed, but at least they are not actively being tortured and are being cared for by zoologists instead of trainers with bullhooks.