If you have never been to Niagara Falls, you should make a quick trip there. The American side is beautiful and if you have extra time to cross over the border, you can explore the Canadian side too (passports required!) Maid of the Mist (boat ride) or Cave of the Winds (be prepared to get soaked) are two major attractions at the falls. There are also a few nice hikes to explore the area. Check out the website for hike options.
Follow the Niagara Wine Trail to try some of the local wineries.
The best place to eat authentic Buffalo hot wings!
Explore the waterfront in downtown Buffalo. Canalside and the outer harbor have options for bike or kayak rentals too.
Explore the art gallery in Buffalo, NY. Nearby is Delaware park where you can enjoy the walking path around the lake and visit the rose garden too.
If you have extra time to explore buffalo, this is a good stop to view the famous architecture of Frank Loyd Wright.