Sorry, you're not getting any concrete answers out of me.... just some strong opinions...
When it comes to team captain, the person should have some leadership skills, but more importantly should care more and put in more time than any other student. An important task got missed by a student, guess who has to cover that without complaint? The captain. It can be a lot more work than students imagine.
As for driver, it should go to the combination of most skilled and best attitude. No sense in a really skilled driver if he won't cooperate with the rest of the drive team, and no sense in a driver that cooperates great, but is a terrible driver.
In both cases, seniority shouldn't matter one bit. If a kid has spent 4 years on the team and there is a sophomore that would make a better driver or captain, tough for the senior.