This is a lovely September break which has you in Toronto for 4 nights, 2 nights in Niagara Falls and then New York for 3 nights. This can probably be replicated at cheaper times such as February but it will be pretty damn cold then! Flights are all with Westjet/Delta which are good airlines and baggage is included. I've also included car hire so you can drive in Toronto and Niagara.
On 18th September you'll fly direct to Toronto with Westjet. You collect your hire car and the hotel I've picked for 4 nights is the Comfort Inn North. This room sleeps 4 people so is large enough and it also has breakfast and free parking. It's not in the centre of Toronto but as you have a car you don't need to be and you could always use public transport if you didn't want to take the car. Head to see some of the sports events Toronto is famous for or head to the lake for some lovely Autumnal pictures.
On 22nd you'll take the short drive to Niagara. I've based you at a really good reviewed place, the Rex Motel which is rated No1 on TripAdvisor but I've also checked the reviews on other verified sites and it comes up really good. Forget places like the 'luxury' Sheraton on the Falls, unless you have a room with a view which you'll pay extra for it really isn't worth the cost.
On 24th September you'll drive back to Toronto (to avoid one way car rental fees) and drop you car at the airport and catch your flight to New York. You will have time to so this as your flight isn't until lunch so there is no rush.
Once in New York you will stay for 3 nights at the Marrakech Hotel on the Upper West Side, New York which is no Central Park. You need to book this using lastminute.com 'secret hotels' but it then actually tells you the hotel name and the description gives it away as it's easy to figure it out! You are ideally places for 3 nights of exploring the bright lights and attractions of NY.
On 27th you'll catch your flight home.
Long Haul flights London to Toronto and New York to London (multistop). Book at Carlton Leisure Club £299.2pp
Car Hire book via Skyscanner £98.52
4 nights in Toronto £201.12 book at hotels.com
2 nights at the Rex Motel in Niagara book at hotels.com £130.99
2 flights from Toronto to New York book via Go to Gate £152.31
3 nights in NY book at lastminute.com using £10 off code on voucher section of HUKD £481.42