It's only about a 20 minute drive. Are you driving yourself? If so, you'll need to park at TTC and then take the ferry or monorail over, which can easily add 20 minutes from the parking lot to the gate. If you're taking a cab, have the driver drop you off at the Contemporary and walk over to MK - only about a 5 minute walk and you'll avoid the hassle from TTC. Either way, I'd leave about 3pm.