Do you have an organized system of chores? What sorts of responsibilities do you delegate and to what age? Do you have rewards/consequences for performing or not performing assigned tasks?
I have three sons, the two older ones are ages 10 and 9. The youngest is 6. When I was facing having three littles 3 years old and younger, I freaked out--literally. I was convinced that being so outnumbered would mean the entire house would go to the pigs, that no one would ever be cleanly dressed or well-fed again, ever and ever, amen.
Thoroughly, even too thoroughly, I embarked on a great "training" program of basic chores. I was pregnant and hormonal and do not recommend this type of approach--that of panic and intensity. Many tears, theirs and mine, would have been saved if I'd been more trusting in God's provision and more relaxed in my approach. God, in His grace, did bless the effort and redeem my mistakes in that by the time the boys were 3 1/2 and 4 and I had a newborn, the older two could get up and dress themselves (from clothes previously laid out) and make their beds (pull the covers up). That was a huge event in all of our lives.
Other things just followed from that. The only way I was able to get anything done was to co-opt the boys into helping Mommy. The chores at first were simple ones, dustpan and short broom sweeping under the table after meals, wiping the table off with well-squeezed out dishcloth, putting the plastic ware in the cabinet, pulling the dirty clothes out of the hamper and into the basket, taking clothes to the laundry room, and so on.
As they got older, ages 5 and 6, they graduated to folding towels, putting away their socks and underwear (because no folding required necessarily), and even vacuuming. Their favorite was to put on their hands an old sock of Daddy's and zip along the baseboards.
Two years ago the chores took on a more regular schedule so that one son, every morning and evening, is responsible for opening and closing the blinds. The other son regularly handles collecting and taking out the trash, to the street. The youngest is responsible for sweeping the kitchen, stairs and foyer as needed. All three boys are required to regularly help in unloading and loading the dishwasher, setting and clearing the table, washing, drying, folding and putting away all of the laundry. These chores are considered the regular and necessary set of things to do to keep the house (and Mom) from falling apart. So these chores are not recompensed with money. Failure to help the family does result in a consequence such as Biblical discipline, loss of privilege, or sometimes even a fine from their banks.
However, there are many additional things that they can do to earn money around the house, such as clearing the yard of sticks and rocks, watering the plants, blowing off the driveway and sidewalk, loading and unloading firewood, washing the car and vacuuming the inside. Dad usually makes that determination of wage and wage earner. He is counting down the days to when they will take over any mowing and hedge clipping.
Another thing we recently started this past year was for my two oldest boys, during the week, to go over to a friend's house who has 3 littles 3 years old and under. They work for her as her mother's helpers. She fills out a paper of their assigned chores and how they performed their work, and then we pay them for their work. Lack of diligence or incomplete work receives a docking of their pay. They love to work for her. They practice all manner of household chore that we've trained in here at home. We're thrilled that they are learning great life skills towards being a responsible man and Daddy one day.
So, Lisa, that's my answer to your question. I know that your boys are different in ages from mine, but my counsel to any other mother who has ever asked is to look at the skills each child all ready has, in playing, and parlay those skills to help around the house. If a child can stack blocks, he can fold towels. If a child can hit a pitched baseball, he can load and unload a dishwasher. If a child can build an intricate Lego model, he can collect and organize the trash or silverware drawer or help make a meal.
The wisest counsel I received from a mom of 7 (5 boys, 2 girls) was to involve the children in useful work around the house. She said that is was not only important for their practical training (knowing how a house runs) but also for their spiritual training. The truth being that the principle of useful work comes from God. He made a garden for Adam and immediately put him to WORK, not to lounging, in it. Useful work builds character and grows each one in sanctification as you both train and learn to be trained in how to do a particular job. Requiring both the mom and the child to trust God's word in 1 Cor 10:31, "So whether you eat or drink or whatever you do, do it all for the glory of God." Also Col 3:23, "Whatever you do, work at it with all your heart, as working for the Lord, not for men,".
Friend, I pray you Godspeed and blessing for your endeavors.