I'm sure you misunderstand Kennedy's sentiments towards children. I believe he is concerned about ANY child currently in his interpretation "in immediate legal harm" from being denied the benefits of marriage. I don't think Kennedy wishes any child to suffer..That being said, Kennedy might want to be concerned about the untold 100s of millions of kids he might inadvertently be sentencing to psychological damage by forcing states to incentivize homes where the complimentary gender as vital parental role model is guaranteed to be missing 100% of the time....structuraly the same as single parent homes (monosexuals) That gender may be the child's own.
He specifically cites the 40,000 children in California who are the children of same sex parents. That defines the group he recognizes are harmed. Any you add to it is your imagination. Not Kennedy's findings or expressed opinion.
Harm to a child doesn't change arbitrarily. If a child is hurt by being psychologically-deprived, another child being psychologically-deprived is in no less harm than the first.
Your willingness to use children to forward your agenda is noted for the record. It is quite obvious to all but the slowest mind at this point that children only get your care and concern when its some issue you want to hold them up and play the violin for.

Otherwise it's "get lost kid, you're bothering me..."
If harm must be done to some children while others receive preference, the lesser of those two evils is to choose the group that is the smallest, so that the smallest number of kids receive harm...with that number hopefully nearing or reaching zero.
Cumulative harm over time. Those will be the keywords at the next SCOTUS hearing on the matter.. and "Children are not guinea pigs"..
Over time, so many many MANY more children will become harmed by a "marriage" a state is forced to recognize that offers nothing more structurally than a single parent home, to the detriment of kids. There is no complimentary gender present for those kids who will find themselves needing that role model.
And then there's the harm to children
over time with the destruction of democracy at its core: state's self-rule on questions of incentives and behaviors/lifestyles their discreet communities embrace or find repugnant. This new precedent of "lifestyles have rights" is a very very dangerous one legally. If those lifestyles are allowed to legally run roughshod over other people's freedom of religion, or over the formative environment of children when a majority finds that repugnant, then what you have with this LGBT crusade is a far more insidious harm than anyone has dared to consider.
Well, I'm daring to consider it and I hope SCOTUS is too..