OK - if I got this right, you are arriving at MIA at 3pm Friday, renting a car and driving to Canaveral...200 miles.
As the crow flies, not that bad of a drive. But let's face it you are gonna hit Miami northbound trraffic about 5pm.....ugh.....
That's not a fun time to hit the highway in Miami. A few years ago I worked in Doral, west of the airport near the turnpike. I was glad I lived south cuz the northbound turnpike traffic was much worse than the southbound.
I'd map it both ways and get listening to traffic reports as soon as possible. By the time you have your car (everything is off-site in Miami, you'll take a shuttle) you should have an idea which route is moving better. Note, for most car rental places the route to 95 is going to be marked...the route to the turnpike possibly not. Most are east of the airport and signage is going to lead you to SR836. East on 836 will take you to 95, west to the turnpike.
Next point, if you do choose the turnpike you only want to take it as far as Ft Pierce cuz that's where it begins to cross westerly towards Orlando. Somewhere along here you'll want to cross to 95 to stay coastal to Canaveral. There are places where 95 and the turnpike are literally side by side.... Jupiter is a good place to cross over
Last point, if you choose the turnpike, as someone mentioned a Sunpass can really speed you thru toll booths. Last I checked FL was not well connected to other state systems so your CA one probably won't help. But, some rental comp's are now renting FL Sunpass ....they just add the tolls you ring up to your bill. May want to look into that.