Trust me, the kids are found within the alley closest to North Boulevard (right before you enter/exit). It's a small alley next to a "1 star restaurant" and a "sleeping skiddo". Going into this alley will locate all kids, taking you into a battle with each kid.
If you need help, this video will help locate it (around the 27th minute).
Other side quests and directions can be found here
Hope I helped! :)