These are CRAZY times & we all know it (well most of us...) Are we even going to have Summer Bands or Football? Safe to plan but gotta be flexible too. Heck, My dad didn't get a full say when I was growing up and most often had to take Vacation time in August. I missed my very first HS Football game in a BRAND NEW Stadium because we had vacation to see my Grandmother in Oklahoma (if at best got to see her once a year). I didn't lose my spot, BIG 6A (former 5A) State Marching Band participant, and I was All-State.
FORGIVE or you WILL be losing more than one student. You can make it all required but in the end you must be flexible. Kids can't control what their parents do (same as band directors can't always control their band kids families - When you do your program will lose).
Words of advise - Been There, Done That!