I second the recommendation for a checklist. Your older child might be able to handle a checklist of his or her own (with reminders to check it coming from you). Having a checklist has helped me remember to do things that I might otherwise forget in the rush of the morning (washing face after breakfast comes to my mind

). I like a morning and an afternoon checklist. They help me get out the door in the morning with everything needed, and they help me make sure that afterschool things happen as they should (homework, instrument practice, unpacking lunch containers from that day, checking bags for notes or finished work, etc.)
Think about tomorrow's lunches while you're making dinner. This way you can steam extra broccoli or make an extra quesadilla or something to use in lunches the next day. I often set aside some stuff for the next day's lunches before I serve dinner. Then I know it will be there.

Get up 30 minutes before you think you need to for the first few days, and get the kids up earlier as well. I like to take a shower first and then go wake up ds. If your kids are hard/slow to wake up, build time for that in. After a week or so, you'll have a pretty good idea of how long it actually takes to get out the door each day.
When you/your children check their bags after school, fill out any paperwork right then and put it back in the bag for the next day. Mark any important dates on the calendar as soon as you find out about them. I also mark down any unusual supplies that are needed for an activity. For example, if the class is going to a pumpkin patch, I might want to send rain boots if it's been at all wet lately. If they need 2 egg cartons, next week, I make a note on the calendar for next week and for tomorrow so I have a chance to find the cartons in time! Will they need a sack lunch for a field trip? Write it down; otherwise, it's too easy to forget on the day of the activity.
If a coat/sweater/lunchbox/boot doesn't come home, try to check lost and found at school as soon as possible. If it's not there, try back a few days later. We've found most stuff does turn up. I also try to remember at pickup if ds was wearing a sweater that morning. This happens a lot in the fall and spring when it's cold in the morning and hot in the afternoon, and checking with ds before we leave school has helped us not lose things.