What is there to do? Hmmmmm
The main street of Niagara-on-the-Lake is littered with various upscale shops where you can pay twice as much as what something is likely worth.
You can check out the Shaw Festival at
Shaw Festival the best of Ontario Theatre to see if something in the live theatre area tweaks your interest.
If history is your thing, you can visit the Brock Monument at Queenston Heights or take a tour of
Fort George.
There are plenty of wineries to choose from. I personally favour Peller Estates and Reif Estate. On the other side of the coin, Frogpond Farm certainly had a catchy name and an organic presence, but the product in the bottle was more suited to brush cleaning than sipping. There's a neat map available at http://winesofontario.org/region_niag.php (broken link)
Hotel properties at Niagara-on-the-Lake tend to charge top dollar; there are much better deals available 10 miles down the road in Niagara Falls. That said, the Prince of Wales and the Queen's Landing Inn are both very nice properties.