I find it most valuable to focus on morning wake-up times and routines than evening bedtimes, and I do start this the week before school starts. This works for us because I can encourage kids to wake up and plan activities to keep them awake, but I can't make them sleep any earlier than they need to, KWIM? So getting up earlier naturally leads to earlier bedtimes. I need this as much as the kids, since I have to get up with them. I am, of course, typing this at 1:58 am, :LOL.
I agree with Lauren, signs and checklists are great in the morning, especially for remembering things like library books and gym day.
I am worried about how to convince my 'can't sleep without mama' 6 yo to go to bed when he needs to, instead of three hours later when I do. He will probably just fall asleep on the couch every night.