I have been a working Mum of a child in Kindergarten and a Stay at Home Mum of a child in Kindergarten, and the homework is not easy on either.
While I was working, my daughter did her homework in the time it took me to cook dinner. I would set her up at the dinner table and would monitor her progress while I peeled the veges or browned the meat etc. If we grabbed take away that night, she would do her homework in the bathroom while I bathed her brothers. I gave her time every night, just most of the time it was not conventional.
Now I am at home and I have three children doing homework. One in year 4, one in year 2 and one in Kindergarten. It is harder now than it was when I just had the one, but homework is still done while I am preparing dinner. The children all sit at the dinner table and do their work. Sometimes they help each other, sometimes I help them.
I believe that children are often given too much homework and I sometimes think it is the parents being graded not the children, especially when you see some of the assignments that are brought into the classroom. You can always tell which assignment was done by the student and which was done by the parents. At the beginning of every year, I tell the classroom teacher that I will not be doing my childrens assignments for them, and that anything handed in will be entirely their own work.
I have on more than one occaison asked for assignments to be remarked when I find out that the assignment that scored the highest mark was one completed by a 30 something year old mother!
You can only do what you can do, but your problem is not only one experienced by working mothers, it is a problem shared by stay at home mothers (who refuse to do their childrens homework) too.