Hi K.,
I'm a home child care provider along with a mother of 4, it might as well be a mother of 8, lol.
The 1st thingis set up the rules. Get a poster board and write them down and post them where they can see them. Also write down what they are responsible for like cleaning their rooms, keeping them clean, putting their dirty clothes in the hamper or wherever they go. Putting their shoes, coats, and backpacks away, etc.
Get everyone on the same page, clearly set the rules and next the punishments for not following through for what they are to do or rules to follow.
Every kid has currency. No matter what it is they have it. For your daughter maybe it's a toy or a stuffed animal, maybe play dates with a friend. It might be the same for your son.
Find the punishment that fits the crime.
For instance 1 I like to use for not putting their clothes in the hamper or where they go is...If I see them on the floor they have to pick them up put them where they belong, pick them back up go put them back on the floor where they were and then go put them back in tghe hamper or whatever. After them doing this 25 times they get the point real quick, they need to put them where they go. You can use this for just about anything.
The other part of this is keeping them busy.
You don't say whether you work out side of the home or if you are a stay at home mom but either way, you need to have them stay busy throughout the day. Make sure they are getting plenty of rest. If they go to school let them know what they are expected to do when they get home from school. If you are a stay at home mom give them a little more structure during the day.