I agree with previous posters about punishments being too long, sweets being an occasional treat, not a reward, and not sending a 9 year old out with a toddler to look after.
You need to take a step back and look at why they are behaving like they are. They need structure and purpose to their day. That isn't easy with a small baby to care for but it is easier than fire-fighting when things get out of hand like this.
Think of somewhere to take them then give the two older ones individual tasks that help get all of you ready.
You need to make it easy for them to behave well and then tell them they have done well when they do.
Punishment breeds resentment.
If your 9 year old is stuck in the house for three weeks she will drive everyone, including herself, potty!
If you send a 2 year old to bed as a punishment she might start seeing it as a bad place to be and then you'll have problems at night.
Try to deal with unacceptable behaviour by letting them experiences the natural consequences. E.g. they can't do x because you can't trust them not to fight while they are doing it, rather than you are punishing them for fighting.
You clearly really have your hands full. Do your best to stay calm and be positive about the good you see.
Good luck with the rest of the day.