I was at Iga-Ueno a couple weeks ago, for the "Ninja Festa".
- tricky to get to (from Osaka), though route is scenic, and was actually the highlight of that trip
- very lame, nothing authentic. Granted I didn't go to the Ninja museum
- shops are scattered in town. Had to look for something ninja related for a friend and it wasn't easy
I guess the only attraction for the the kid is to dress up as a ninja, only available on weekends during the fest which ends in May.
There is of course the castle. Didn't bother to go inside.