Does mindfulness meditation work for highly inattentive individuals?
The most up-to-date research I can find at the moment specifically looking at children with ADHD is a systematic review and meta-analysis by Chimiklis et al (2018), and they point out that yoga, mindfulness and meditation should not be considered first-line interventions for ADHD but may help and more research is needed.

Considerable risk for bias was found across studies. Given significant methodological limitations of the literature, positive effect sizes found in studies should be interpreted with caution; these interventions should not be considered first-line interventions for ADHD. However, preliminary findings suggest yoga, mindfulness, and meditation may be beneficial for youth with ADHD, but extensive research is required to validate the efficacy of these interventions.

References
Chimiklis, A. L., Dahl, V., Spears, A. P., Goss, K., Fogarty, K., &amp; Chacko, A. (2018). Yoga, mindfulness, and meditation interventions for youth with ADHD: Systematic review and meta-analysis. Journal of Child and Family Studies, 1-14. 10.1007/s10826-018-1148-7