Are parents allowed to drop a few things off on september 1st if one of my parents can't make it on the 30th? Or should I wait until classes actually start?

If your move-in date is the 30th and you've already moved in, your parents will absolutely be able to drop things off on the 1st.
If you're at an event during the time your parents need to drop something off, just let one of your reps know!

Hope this helps

okay thank you!

Your parents can drop off things anytime after you move-in, no worries. (They may have to pay for parking however)