Your job is to provide a quiet place and time for your kids to do the homework, and answer reasonable questions. I would have a conversation with aftercare, they should provide a time and an appropriate place for your school aged child to do homework. If he cannot do the homework without parent intervention, and you feeling like this is your assignment that "we" have to work on, then that is not appropriate. Home work is there to reinforce what they learned already in school and promote independent working skills. If your child cannot particiapte independently, ask them if it is the homework, or your child that needs evaluation. You should not be doing the homework, your son should be able to do the homework, and if the expectation is different, then it is inappropriate. If the homework is appropriate, then the school has to find out how to help your son access homework, not you. This is a school issue, but one that they school will let you sholder if you let them. It is one of the very first indicators that a child has a learning issue, so take it very seriously. It is also the primary way that schools blame parents for learning issues that the school is responsible for remediating. Plain and simple, the first thing I tell parents who are fighting with a school to recognize that their child has a learing disablity is to quit doing the child's homework and keeping the child a float because the school will be very happy to let you do this and not help your child with the real problem for as long as you will do so. I am not saying that this is the case here, but many begin this way, so be aware.
As for your 4 year old, I would not even try to help them do homework. It is totally unneccessary. 4 year olds do not need preschool at all, they could have zero formal instruction and sail through kindergarten, so projects and such are just crazy. First, it is developmentally inappropriate, and second, it will not help your child be ready for homework when it is time for them to do it. Soon, we will be teaching kids to walk as newborns to get them a leg up...it just does not work that way. There is no evidence that any early learning accelorates a child beyond where they would be by the time they enter the 4th grade no matter how much you try to cram into them way too early. If I were you, I would find a play based program that actually provides a developmentally appropriate program for your younger son. He should be read to, playing, singing, and doing art projects that expand his fine motor skills at his developmental level, which does not include any long term planning whatsoever.
I would say, your 4 year old is overdue for some good playing, and your 6 year old should be getting a quiet place to do his homework, and an adult to answer reasonable questions at after care, and if you still find yourself needing to monitor due dates and see that they can manage what they have, it is either inappropriate, or your older son is telling you that you may need to let the school intervene, because it is a school issue.
M.