Not stepping on Chefboyardee - perhaps you have recently launched at Port Mailtand? - but I read a post recently that Port Maitland ramp - WEST side of the Grand is NOT open. The roads in the area were closed and I read they weren't opening anytime soon. Perhaps something has changed.
From Halidmand County Website:
Boat launches – Saturday, May 16, 2020
All public boat launches EXCEPT the Port Maitland West launch (accessed via the Esplanade) will be open for use starting this Saturday. Port Maitland West will not open until piers and beaches are open for normal public use. Docks will not be put in immediately as they require inspections and seasonal maintenance, which will take some time.
I would suggest calling Halidmand County and verify the launch is open - save you a wasted trip in the event.
Cheers - Balleye2