Park at the bottom of Leslie street and walk in, the parking lot not open till 9am but the park is open by dawn or so, noone will bother you on a saturday or sunday. I have been there many times 7am or earlier
Try the base of the spit, when you enter the park look for a big wood sign, there is a trail going off the right that will lead to a nice woodlot, can be some good late migrants in there, after there swing back to the road and go onto the spit, any of the peninsulas are good for birds and at the lookout by a little red bridge will be able to see the comorants and egrets nesting.
Too bad not going on the saturday ,this saturday the 29th there is a field trip at the Leslie Spit being put on by the OFO (Ontario Field Orinitholigists) ,is the largest birding group in Ontario, will be some expert help at that trip