Unless you all have visas, I would have to say (unfortunately) skip Niagara Falls. The Canadian side has many cool things to do, and places to visit. The American side is an absolute disgrace, unless you get into serious potholes and run-down neighborhoods and a huge casino.
Hershey, on the other hand is one of the great family vacation treasures in this country. The park is among my favorites, and the zoo is accessible from the park (small, but nice). Chocolate world is accessible from the parking lot to the park, and is a cool little tour - and the shop and food area is great! The outlets are a great place to walk around and shop. And, while you're in the area, you HAVE to tour one of the Amish farms, and understand how traditional Amish people lived; and visit an Amish buffet or restaurant.