[Billfred]

We're a 4-H team, and any adult volunteer that has passed the screening process is allowed to drive kids (subject to the rule of three). This usually comes into play at regionals, where we often caravan and some parents will take a few other kids along with their own.

For less-official events, we'll usually say "arrive at X at 8:00" and leave it to the kids. This seems to work well too.

For robot transportation, it's almost always a parent with a truck or trailer. I think we've rented a cargo van twice in our history when that fell through, which mentors drove.