The paper includes guidelines for youth resistance training, benefits, the evidence regarding any risks, and injury prevention. If you are having your children lift weights (which is totally appropriate), you should read this and follow the principles.

https://www.shapeamerica.org/publications/resources/teachingtools/coachtoolbox/upload/NSCA-Position-Statement-on-Youth-Resistance-Training-English-2014.pdf

"From a public health perspective, it is noteworthy that traditional fears and misinformed concerns that resistance training would be harmful to the developing skeleton have been replaced by reports indicating that childhood may be the opportune time to build bone mass and enhance bone structure by participating in weight-bearing physical activities.95–97 Fears that resistance training would injure the growth plates of youths are not supported by scientific reports or clinical observations, which indicate that the mechanical stress placed on the developing growth plates from resistance exercise, or high strain eliciting sports such as gymnastics or weightlifting, may be beneficial for bone formation and growth.29 98–102 While children have a lower risk of resistance training-related injury to joint sprains and muscle strains than adults,103 attention to initial postural alignment and technical competency during all exercises throughout the training programme is essential to ensure safe and effective practice irrespective of resistance training mode."