This one ☝🏽… Run of the mill synthetic iron supplements are not generally safe. They are pro- oxidants. (Rather than anti oxidants)
If they are eating rice you can start boiling quinoa and adding it to the rice, they won’t taste it because of the rice (especially if you mix it with other food). Sneaking spinach into pastas also helps
https://www.iherb.com/pr/floradix-floradix-iron-herbs-liquid-herbal-supplement-8-5-fl-oz-250-ml/106339?gad_source=1&gclid=Cj0KCQjwi5q3BhCiARIsAJCfuZl2Sgt3f6pgB8wmf88qwDAE4s0BKB0AjhGSz_AsHK_5nSwD4Apz-bYaAvNoEALw_wcB