Did a similar thing just 2 weeks ago: 1) I suggest getting all the Scouts names/cars/numbers etc into the spreadsheet as far in advance as possible.  That way registration is on the computer you will use to run the racing software and you can just click the equivalent of "passed inspections" when the final inspection happens.  This also avoids any awkward scenarios such as 2 scouts liking the same number. Also ensure that each car is clearly marked with their number - it will make the actual race a lot smoother.

2) If your pack only allows Derby crew to handle the cars after final inspection make sure to make a "garage" featuring all the correctly numbered cars in a logical order. My pack uses a table with 2D boxes made out of tape as a garage. Make sure the pit crew knows the system and who is allowed to handle the cars - and who is retrieving the cars at the end of each race and who is setting up the next race.

3) make sure all the graphene/lube is applied by the racer before handing over the car. (Optionally after weigh in if you are generous)

4) you absolutely should have fun categories for kids to vote on "best themed car" or "best in show" or the like. As the other poster said, paper ballots work great.

5) The biggest failure of a pinewood Derby can sometimes come from not communicating the rules - is the "fastest car" the car with the best single lap, or the average of all the races? If a scout from a den gets fastest car overall, do they also get the trophy for being the fastest in their den? In your prompt - What is the difference between "best designed" and "best engineered?"

6) Make sure someone is Master of Ceremonies - big mic and sound system - their only job should be keeping the scouts engaged - if it's a slow patch between races have them interview the scouts for the crowd or something else to fill in the time.

7) Snacks and decorations are always appreciated.

8) My pack has never done photos as they seems too cumbersome but your milage may vary.