Knowing fully well Maid of the Mist etc will be closed for the season, my family and I still planned a visit here in December, because the state park itself is open year round. It wasn’t too busy, and we found plenty of parking - $10 per vehicle, and valid for the entire day, even if you move from parking lot to parking lot.
The gift shop was a tad bit of a let down, but we enjoyed the falls from Prospect Point. The evening illumination and 8 pm fireworks were worth the repeat visit in the evening.