What are your goals for the activity? To entice them into a career?
I can't think of too much that's appropriate to such a large range. Maybe something like bringing samples of different types of pill bottles and warning labels to teach them how to read the warnings, for the little kids to teach them to stay away from prescription medicines, and for the older kids to teach them the types of bottles that might be useful to keep from confusing medicines that they can tell their grandparents about, or to help them better understand what the warnings say? Basically, they shouldn't need to use it, but maybe along the lines of showing them things that might help them deal with an elderly relative or family friend who needs help keeping track of many prescriptions?
The kids might find it interesting to see something about how capsules or pills are made...if you have empty capsules for a show and tell activity, that might be interesting (as long as you're not teaching them how to better prepare their illicit drugs :uhh:).
Most of the science side of it is likely over their heads.
Though...hmm...what about showing them how time release or buffered coatings work? If you have the materials for it anyway. For example, the coatings that dissolve in your mouth you could show them in a solution to mimic saliva components, and ones that start dissolving in the stomach you can show in a "stomach" solution, and lower in the intestine, etc. This would come with a little bit of science lesson about the digestive system too.
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