Cheap Packages From Toronto To Las Vegas?

My girls and I are planning a trip to Vegas in early May (probably from the 2nd to the 5th). What and where would be the BEST prices to find a deal on the flight and the hotel (somewhere on or near the strip)?!?
Any recommendations on whether we should by last minute or not? Also, I’ve heard that leaving from Buffalo would be cheaper. Any suggestions on that?
Thanks!!!