The northeastern end of Lake Ontario is pretty good at creating big waves. Beyond the obvious things like dressing for a long swim in cold water and practicing rescues, I think the biggest item on the prep list should be a plan B. If the weather turns the wrong way, the lake will kick your ass, so you may have to just sit and watch the wind for a day or two.
You might be able to choose sheltered routes depending on the wind direction, but I don't know if you'll find satisfactory options for that. My introduction to kayak surfing occurred in the Thousand Islands, well off the lake, and downwind of only about 5 miles of open water in a decent breeze (maybe 15 knots?). It was fun for a few minutes, but exhausting to make any distance into or across the wind. So I'd suggest accepting that even moderately bad weather could make portions of the trip impossible and planning around that. That means extra food and extra time in the schedule or a route that allows a mid-trip bailout.
Actually, now that I think of it, that bit about cold water deserves a bit more attention. Lake Ontario is unusually fond of producing upwellings of cold water around its edges -- the cold lower layers slosh around with wind and atmospheric pressure variations, and once in a while some of that cold water sloshes right up to the surface near shore. Surface water temperatures can drop from the 70s down to the 50s in a matter of hours, so pack cold-water gear even if the reported surface temperatures are warm.