They should be present anyhow. A town or village or any settlement really feels much more alive and believable if there's every day stuff going on like women hanging up laundry and kids getting under everyone's feet.
Kids present is a cheap, easy but major boost to immersion.
I'd understand if in the end kids were unkillable but if you include them in the first place then immediately break the immersion of the game by having them frolic along as everything around burns to the ground without a scratch on their head...then I think it would be better to not have them at all.
Would make a great mystery though no? You see a village on fire and then a kid rolling around in the flames oblivious.
