Well going to both of those places, A LOT, sometimes more than once a year each... It depends if you bring your son...
Because there is an entire long street dedicated to entertainment, most often geared towards kids.. I spent a lot of time there, with wax museums, horror houses, arcades by the million and little random rides.
In Niagara we always obviously go to the falls, but there are also different activities to do with the falls... There is maid of the mist, where you ride right up to them and get SOAKED, journey behind the falls is pretty cool, but not as fun... Uhhh, there are butterfly exhibits and Niagara on the Lake is a beautiful town my family often takes a detour to.. It's famous for their wines and they have this big whirlpool we always visit.
In the winter they have the falls lit up different colours, and it's very pretty... so if you go in the winter get a fall view hotel room. They sometimes have fireworks in the summer too.
Then for you, there are a few casinos and I'd assume lots and lots of bars, restaurants, night clubs ect. There is probably a lot of stuff even I haven't done... It's a pretty fun place
Then in Toronto, I know a lot as well XD let's see.... CN tower is very cool to go up, you get to look through the glass window, so freaky, and there are look-outs where you can see all of Toronto. As well, in the CN tower there is a revolving restaurant.. I was too young when I went there to remember the food, but the view was a amazing, and the entire restaurant slowly revolved. So be sure not to leave your purse on the little ledge, or it will be a few tables down ten minutes later XD Also, when going to the CN, don't go on a foggy day where you can't see anything T__T that's a given though.
THere are LOTS and LOTS of theaters where I've seen everything from Mamma Mia, Sound of Music, Lion King, and children's disney plays. Book ahead for those and get tickets. They have tons of fancy restaurants with foods from all around the globe, and also of course, a lot of Pizza Pizzas and such.

What else about Toronto.... Hmmm.. There's lots of shopping, the Eatons Centre is a pretty big mall, me and my friends go to a lot... there usually street art there (for some reason I find that stuff so cool XD)
There is also Centre Island, a little Island with a kiddy amusement park. But if you want a REAL amusement park go to Wonderland, it is not downtown... it's near... gosh what's the name of that place D: Vaughan or.. I dunno, something like that.. It probably has a website with directions

they have a big water park, rides, roller coasters, kids rides as well, LOVE their funnel cakes.. They have shows and cliff diving, and of course.. candy shops!
If you go around Halloween they have the "Halloween Haunt"... it's got rides open, but also lots of haunted houses, and people dressed in masks creeping you out... The haunted houses were actually terrifying 0__0 even for me who usually doesnt get bothered by that type of stuff... I was screaming at my friends who blocked me off from running away, and I had a guy with a chainsaw coming after me. XD
So yea.... Toronto and Niagara have a lot to offer ^^ And a lot I've probably never done or mentioned XD I'm not sure about the prices, as I'm not old enough to know what's spent/ But I do know there is some REALLY expensive stuff, but also really cheap ways to have fun
hope this helps?