When we took the 4 grandkids there last year we stayed at Branches of the Niagra Camp Ground. Great place.
To do:
niagra falls - canadian side cave of the winds (american side-no cave-$100pp or more)
Teddy Roosevelt Nat Historic site -
Buffalo Three sisters island
Welland canal - niagra on the lake west across canal. Head south on parkway. Lock 3 has museum, viewing area etc.
Letchworth State Park
Ontario Science Centre - 770 Don Mills Rd
Toronto Island Martin's Fantasy Island - good for young kids since they have many rides for the small ones too.
Fort Erie
Lockport,
NY Ripley's Aquarium Toronto