This is a great idea and initial execution. Consider K12 carpooling as well.

I've got kids in middle and high school, and in our community most of the kids get to school and home via carpools. My wife did most of the driving, and it was a perpetual headache for her. She'd forget when it was her day, kids would get sick and need to cancel pickup, or kids would decide to walk home. Parents would trade driving slots and then no one else would know who to contact when things 'came up'.

We're not carpooling this year, but she would have loved group messaging (msg parents, msg kids, msg all) and the roll call features. She also would have appreciated it if you guys kept track of who was driving and if she got a text message 30 minutes before it was her turn to drive.

Congrats!