Are we talking about 8 year olds, or 15 year olds?

I think it's fine to give your 8th grader a flip phone. A third grader isn't "grabbing dinner after band practice".

For sports practice, I'd just take the sports bus home; the 30-60 minutes between the end of practice and the time the bus left was perfect for a little quiet reading or homework.

For band practice, I'd call my parents from the office phone, or plan to get a ride home from an older student who lived nearby, or just accept that I might miss out on something when mom picked me up at 6:30 and that's ok.