You could include corn grinding. Get regular popcorn to grind. Find a large, flat stone (about a foot square gives you plenty of room) and a smaller, crushing stone. The kids then crush and grind the popcorn between the
stones. This was one of the activities we used at the museum where I worked. Beware, though, that the crushed corn really can't be prepared as food. Tiny bits of rock stay in the mix, which, in olden times, wore down the teeth of the native Americans who ate it.
Some other work that would have been appropriate to long ago children:
sewing weaving washing clothes by hand carrying
water (you could do it outdoors...) cooking and baking beading tending animals or younger siblings
Any of these might be adapted for your work day. Have fun!