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Don't forget your passport (or Enhanced Driver's License) if you plan to cross into Canada, and you can walk across. Not sure where you plan to stay, but Niagara Falls NY is a bit seedy and rundown as soon as you get away from the falls and casino area... The Canadian side is much safer feeling, IMO.
Also, when are you going? The Maid of the Mist is not year round and is currently closed for the season (according to their website). Regarding the mist, yes, depending on the wind, it will drift over the observation areas. In terms of best timing for light, in the morning the sun will be shining on the Canadian side on the west. In the late afternoon it will be the opposite. If you want sun on the horseshoe falls, I think you need to be on the Canadian side, and at this time of year, mid afternoon because the sun sets pretty early. But I'm not sure that the sun will come around enough to shine on the horseshoe falls.
For NYC those lenses will cover your basic needs. You could also benefit from a longer zoom, but if you don't have one, you will still get by fine.