my process for this would be something like, identify the national organization which has championed your issue best, I would normally expect the ACLU to be on top of this, but it looks like they haven't put together a national response like they have for other issues, like protecting trans rights, abortion access, even stuff like "right to learn" preventing censorship in education, etc. I'm seeing scattered statements about undocumented children in terrible working conditions, but nothing about the child labor law issues yet. Local chapters do cover more issues, especially if something is having higher impact locally, so it's worth seeing if your local chapter has started working on it. If not, maybe give them a call or an email. They'd love to hear what people in their operating area care about, maybe someone on the inside has been pushing for a response but hasn't been given any resources to go after it because they're not sure if the public support is there. And perhaps they'll direct you to an organization that is working that issue locally.
Exhaust all potential experienced coordinators before moving on to setting things up yourself. The resources and general know-how that experienced activists can bring to a movement is invaluable, even just offhand comments from such a person can help you avoid common pitfalls and see a lot more success in your protest.
Beyond the ACLU, maybe check out if there's any particularly strong unions in your area. Unions generally aren't as big on activism as they once were, but this is a serious worker's rights issue, and also threatens their bargaining positions by increasing the labor supply. The AFL-CIO seems to be pretty active in opposing the weakening of child labor laws in Iowa, for example.
anyway I'm talking a bigger game than I actually have experience with lol, but I hope this is helpful. Good luck! I bet cohost would love to hear about your experience on this. :) I know I would!