My recommendation is the Genesee Falls Inn
in Portageville. I've stayed there several times. Built in 1870, the entire hotel and rooms maintain a Victorian decor. It is a bit rustic, but the beds and plumbing are modern. They also have a house next door which they will rent to larger families or groups. The staff is friendly and helpful in the extreme. The wifi wasn't working when I was there a week or so ago, and also was out when I visited a couple years ago, so I wouldn't count too heavily on that. But they have a huge collection of DVD's you can pick from and take to your room (no charge), and a collection of board games. They also have a 7-seat conference bike you can pedal around the neighborhood (2 kids and I took it for a spin last week), and kayaks you can take on the river. Breakfast in the morning, and if you need to leave early, they'll leave the kitchen unlocked and show you what's available. Very informal, but very, very cool place to stay.
Be advised though, that the only place for dinner in Portageville is the Letchworth Pines
. I've had good food and drink there before, but this time when we arrived 10 minutes before the scheduled close of food service, the kitchen was already shut down. However, a very nice waitress pulled together soups, pasta salad, and ice cream dessert for me and the kids. The Pines also has a bowling alley, and a good selection of beers. On weekend evenings there is a chance of live music or bad karaoke (Is there such a thing as good karaoke?)
There should be other places to eat in Nunda, a few minutes to the east.
One other note, the south (Portageville) entrance to Letchworth SP is closed, as are the trails and viewing area for the upper falls. Its not far around to the main entrance, but I was disappointed not to be able to get the kids to any place where we could clearly see the upper falls - seemed like they could have done a better job preserving access while re-constructing that area. I presume event officials will post any updates if that entrance or viewing area opens back up - I am not sure what the completion schedule is.