You are renting the car that morning? Or the night before? Either is fine, but it might effect your timing.
Look for a rental company that doesn't charge extra for a one way trip. Most do not charge extra.
You should be able to reserve a car without putting any money down. That way, if your trip gets postponed or canceled, you aren't out any money.
Depending on where you pick up the car, and what time of day, there may be a line at the counter to pick it up, so plan for that. Could be 5 minutes, could be an hour.
The drive from Orlando to PC takes about an hour. There are two $1.25 tolls (unless they went up recently) on the way. You can either bring quarters for the toll or use the rental companies electronic device, but if you do that, it will cost something in addition to price of the tolls. (For Budget it was $4/day).
Once you get to PC, you drive to the rental car place and return the car. That part is quick. People returning cars can often get in a shorter line. Taking their shuttle bus with your sons and your luggage may or may not be quick. Luck of the draw. Might take 10 minutes, might take 45 minutes. Once on the shuttle they will take you in the back entrance and drop you off near the ship, no problem, where the porters will take your checked bags and you can start the check-in process.