@ravisurdhar Double check with the ferry and rental cars....the suppliers I work with always have my clients drop the car...I have a vague memory of a conversation why and the answer being an extra fee. Just make sure you are aware.
As far as drive times, I stand by my statement. With it being a high tourist season, the traffic will be slower. Additionally, the OP's estimates of drive times were low to begin with. Every client I have ever sent all said the same thing, the drives were longer than planned for. I found that to be the case when I was there as well.