B.C.
The Canadian side has a lot better view of the falls and has more to do.
(The American side park is ok but many area attractions have closed an it's kind of a run down area.)
There's the Rainbow Bridge that you can cross right there but I've never used that one myself.
Bring your passports.
Since my Mom lives south of Buffalo we always use the Peace Bridge in Buffalo to cross back and forth.
There's Marineland (part zoo part amusement park) - that's a whole day of walking in itself.
Maid of the Mist boat rides are available from both American and Canadian sides.
There's the Butterfly Conservatory, the Botanical Gardens, and many other things to see.
http://www.niagaraparks.com/niagara-falls-attractions/but...