Love Niagara Falls! I recommend the Canadian side also, we've always found it to be more up kept and you have a better view of the falls. We stay at Sheraton on the Falls also and like it. It's worth getting a view of the falls in the evening so you can sit and watch the falls all lit up. They look so pretty and it's romantic in the evenings.
If you like to see the natural wonders, then get a Discovery Pass
http://www.niagarafallsstatepark.com/PassToTheFalls.aspx So much fun!
Also, I strongly suggest going in the September/October months. Not so packed and still not horrible weather (usually).
Try the butterfly conservatory, it's one of the best I've been too, and we've been to many. None ever compare to that one to me.
Clifton Hills is where all the fun is
http://www.cliftonhill.com/ in the evenings.
I hate to say this, and maybe it's just our taste but the food in Niagara Falls has never impressed me, so I won't suggest any places to dine at.
Even though I suggest staying on the Canadian side. I still suggest going to the park on the American side just to look at the falls from that viewpoint, it's amazing looking at the falls from all angles!