I enjoyed this expo the same as the Dino expo last year because it's not crowded. Mammoths aren't the draw, compared to dinosaurs but if you or your kid is into mammoths and other prehistoric mammals, why not check it out?
Place: Ueno park
Admission: adults 1600 yen, elementary aged kids and up 600 yen. Small kids free.
The first part is disappointing, as it is just fossils from mice and small mammals and such. See below:
My husband and I were not impressed with the tree bark and leaves impressions but the giant mammoth and other mammals made up for it.
I suggest doing a bit of research as a family together before coming so you can appreciate what it has to offer.
Photos curtesy of my 6 year old. :-)