You don't need to do all that, but you do need to tell them you aren't. It's not fair just to not do it.
At that age I usually knock once on their door to tell them it's up time. I then get me up and they get themselves up. They know the time I leave and they need to be ready by then, and yes, I have driven the car down the drive without one (dh was still home), although they caught up as I turned the car round.
Occasionally I get a "oh bother mum I forgot to say I need..." moment. They know that unless it's quick (or totally essential) then it won't happen in the morning.
Ds is quite capable of doing everything and walking out to the car without his bag (he has ADHD) but that's another story. He normally realises before we leave.
Tonight, while things are calm, tell them that from tomorrow you expect them to get their clothes/bags etc ready the night before. You'll knock on their door at whatever time you're up, and give a final reminder knock when you go downstairs. You will leave at X time whether or not they are ready.
And do it (within reasons obviously). Tell them if they don't leave with you, you will phone the school to tell them exactly why they are late (didn't get up). Can your dh take them to school late if necessary?