Password protection is easily circumvented. If your children (I assume) know how to open the options and remove the keywords from the filter, - it won't take them long to find out how to edit the limewire.props file (or they'd ask somebody in here how to do it). It'd be possible to set the filters to always enabled by editing the LimeWire source code and compile a customized version, but I don't think you'd want to do that...

So enable the filter and don't leave your kids alone with the computer.