This is one any breeder with kids is going to struggle with, in the end you have to come up with where your priorities are, are you in it to show or to sell because you really can't do both.
Mike Hartman's kids were very competitive showers as they were growing up, but you didn't see them dragging Maines, and as a breeder I think that is a great business plan, most customers aren't very happy when they get beat by the person that sold them the calf.
We raise cattle to show, every calf in our barn has a price and they are all for sale, but the ones we really want to keep are priced accordingly, if you want them worse, you will pay for them.
I guess I don't have as much of a problem with people showing their own as I do the people that sell me a calf and then go out and buy a better one in the same breed/age group, that leaves a very bitter taste! If your calves aren't good enough for you to show, why do you think they would be good enough for my kids to show.