I'm gonna fire out a few ideas for this park and hope that Nintendo steals them.
It appears from the teaser vid and current speculation that the park will have a Mushroom Kingdom type area where visitors can walk around, meet Mario characters, and likely shop in Mario-themed shops. That would be nice, but what would be even better would be a Legend of Zelda village area. How cool would it be to walk around a Kakariko Village inspired area, browsing tiny shops and talking to costumed shop keepers. Very cool (except for the lines).
Also, it's not Nintendo's most popular IP but a Star Fox ride would have tons of potential. The "easy" way to do it would be to set it up like a modernized Back to the Future ride, except with a 3D screen and Arwings instead of DeLoreans. Each Arwing's lasers could be seen firing at the screen and just like the game, the enemies each player hits would blow up, making the ride a shooting competition among visitors. The harder, but potentially cooler way, would be to set it up as a full VR ride, with the Arwings being purely for motion. Making it VR would open the interactive possibilities wide open (not to mention allow more participants at once).