What is the best VFR route to CYKZ (ButtonVille) when approaching from the southeast?
I fly out of CYTZ and know the area fairly well. A few things to keep in mind. If you'd like to transition through CYTZ airspace to Buttonville, you'll find controllers there pretty accommodating. Getting in touch with Toronto Terminal is not a problem, you're not asking to cut through Pearson, but you'll be sticking along the shoreline so I wouldn't worry too much. 

I would recommend against flying at 1700 feet. That's awfully low. Here's what I would recommend.

Get a VTA sectional for Toronto. This will have much greater detail for the area as well as recommended VFR routes. 

Hug the coastline at 2500'. Contact Toronto Approach at 133.4 before entering the zone. Ask for clearance through the zone to Buttonville via the shoreline and city centre. Follow the coast line until you're about 10 miles outside of City Centre (YTZ). There Approach will transition you to Tower if you're at 2500 or below. They will clear you to Buttonville by staying east of the DVP/404. That's the major highway cutting N/S through downtown, east of the airport. Once you're clear of City Centre, you'll get passed over to Buttonville for your landing. As long as you follow DVP/404, you'll find the airport easily. I believe there's a landing fee as well.