Wow! What a challenge! But focus on the good things. It will be easier for you to step in with boys rather than girls. You have them full-time so there is no one else to undo what you're trying to do in raising them!
Before you try to "put your foot down" be sure you have their respect and appreciation through a positive relationship first. Here are some ideas:
1. Make time with you positive. Be supportive. Listen to what they have to say. Joke around and share laughter. Take them for fun times when possible. Be involved in their lives.
2. Be consistent and even tempered. Do NOT yell or get mad easily. You don't have to yell in order to get what you need from them. Make it clear: Be nice and we all spend fun time together OR go to your room to be alone. Make everything a teaching/learning experience.
3. If he gets mad at you, don't get mad in return. Just say, "If you're mad at me, you can go to your room to cool off until you decide to come out again." Repeat as necessary. And say, "OK, if you don't listen to me, I'll have to tell your dad (in an omimous voice)" or "I really wish you'd listen to me because I want you to be able to have fun with us. But if you don't listen, you'll have to go to time out in your room. And we WANT you to have fun with us!!!"
4. Keep your directives and rules to a minimum. No one likes to be bossed around. Our "rules" were simple: No hurting and everyone helps because we're a team.
All the kids are at an age when they can understand why they must do what you tell them. "Brush your teeth or you'll have cavities and need to get shots at the dentist."
I also took the time to explain that they must trust me. There will be times when I can't say, "Please get out of the street because a car is coming and you could be smashed and end up in the hospital with crushed legs....blah, blah." They must trust me when I shout, "MOVE NOW!"
I also made it clear that I LOVE THEM and only tell them what to do when it is for their own good. NOT because I feel like bossing them around. Let them know that you love them and it is your job to protect them and be sure they grow up to be good adults.
Explain things to your kids all the time. Treat them with respect and let them have choices (you choose their options) to show them you do respect their wants and their ideas. Don't use the "Because I'm the mom and I said so" line. Always have a good reason for laying down a law and be willing to explain it.
5. Give them rewards for being a team. Explain how doing chores is doing something good for the family. Say "thank you" a lot and praise them for doing good things (helping each other, being kind, getting up for school without being nagged, etc.) Rewards don't have to be huge or costly. You can make a game out of chores or use a simple chart. We had a 15-minute blitz where I'd set a time for 15 minutes and we'd go around like maniacs (one person picked up laundry, another picked up any dishes, another trash, etc.) Then, we had a nice reward: a picnic, movies out, ice cream outing or a movie night in.
6. Play with them. That is the biggest thing parents forget. Play with them. That is bonding time. And if they bond with you, they'll love and trust you forever.
Hope this helps! I wish you well!