One is plenty.

You may then wish to include a visit to Niagara on the Lake that day. Then return to the falls to see the lights in the evening.

We go for a weekend at a time, so 2 days total and find plenty to do between Niagara Falls and Niagara on the Lake.

Another factor... how long do you want to spend in a casino.

And... do you want to go to a play in Niagara on The Lake? That could add an evening.

It's only a couple of hours at most from Niagara Falls or Niagara on the Lake to Toronto, so you could enjoy a play and then still drive to Toronto, checking into your Toronto hotel before midnight.

BAK

Make sure you take your son on the big three attractions at the Falls... Maid of the Mist... Cave of the Winds (US Side) and the best of all Whirlpool Jet Boats...

I would suggest you decide exactly what it is you want to do in Niagara Falls before deciding how many days to spend there.

Here is a link that lists the Canadian side attractions: http://www.niagaraparks.com/

Here is a link that lists the US side attractions:
http://www.niagarafallsstatepark.com/

The first time I went, I followed the "one day is all you need" rule and felt like I didn't get the chance to enjoy it. Others spend a day there and can't get away quick enough.

Figure out what attractions hold an interest to you and then figure 1-3 attractions per day. That will tell you how long you should reserve for Niagara Falls.

20 minutes.


only half kidding - niagara falls is very much like a cheap version of atlantic city (if you know what i mean) overpriced crappy restaurants, cheesy tourist attractions etc... the falls themselves are beautiful, but after a few pictures and a coffee on a park bench watching thats about all you need.

that said, niagara on the lake area and the surrounding wineries are great - we go out often for day trips from toronto, but could easily spend a weekend there (if you're into wine / food)

have fun