A stronghold is like a habit of the mind - a way of thinking that you don't even think about. The only way, then, to think about, is to either have another person point it out to you, or the Holy Spirit points it out to you.
Your kids are beginning to have strongholds created in their minds - way to act, react, their self-image, or even about others. Right now, some might even say are "cute" or "just kids", but are they the kind of strongholds that we want established in our kids? If no, then let's work with them (in love) to demolish them by speaking God's Word about those areas until we believe them!