Traffic in the airport and Disney area can vary a lot depending upon the time of year and the time of day. It might also help if we had a better idea of where you were from in so much that we might be able to better gage what you are used to as far as traffic. (Obviously, Traffic in places like Atlanta is going to be much different that traffic in Gettysburg, PA).
That being said, Traffic between the airport and Disney isn't too bad. The signs and interchanges are also very well marked out and so you don't have to worry about accidently missing your exit.
Tolls, I think there is like a $.50 toll between the airport and I-4, so if you have even $1 on you after your flight, you'll be fine. Your rental car agency will likely offer a pass, but they often charge you a base fee per day to use the pass, plus the tolls incurred. The $7 charge to use the pass may not be a big deal on days you are making the trip to the space coast, but on a day when your only toll would be a $.50 charge to get to the airport, it makes less sense.