I see no reason why Algin could not be taken by children...it's just a fiber source...as long as they can swallow the capsules. Another member of this forum was giving it to her 9 year-old to help with mercury poisoning from vaccinations.

If they can't swallow capsules, you could try opening the capsules and adding a little of the Algin powder to applesauce or juice, etc. You'll have to experiment, because Algin is quite a thickening substance...it doesn't take much to end up with a thick gel.