It's the restaurant's right to do this, so I've got no complaint about it. I'd just eat elsewhere, with our without my kids.
I will say that I applaud management's decision to be forthright about its feelings on the topic. Too often I've gone into run-of-the-mill (i.e., not fancy where children wouldn't ordinarily be guests) restaurants with my kids only to get some snide comment from the host/hostess/manager/owner. In at least one case, we all turned on our heels and left based on some sarcastic comment made by the staff about dining with children. If management doesn't want to host them, just adopt this place's policy.