For largemouth I would put in @ Poonamalie Locks just on the outskirts of Smiths Falls off Highway 15 going towards Portland. The water from the locks till it starts to open up into the Lower Rideau is heaven for largemouth fisherman. The channel is well marked. PLEASE be careful out of the channel. You may want to consider getting Chart 1513 Smiths Falls to Kingston. A few Km's past the Poonamalie Lock road going into Smiths Falls will get you to Bennett's Bait and Tackle.
For lakers and smallies launching out of Portland is your best bet.
Hope this helps,
DropShot'r