When you start to feel this way, ask yourself this question. Would you rather your children remember all the times you were late to dinner, or missed dinner altogether because you were busy at work. Or would you rather your children remember you fixing a homecooked meal with a smile on your face because you are doing your dream job -- raising your family. Your children wouldn't remember all the time that you spent at work to try to get them more "things," but they are sure to remember all the special moments that you missed because you were at work. Even if it was something as simple as one of your children earning 100% on their spelling test and wanting to come home to your loving arms and tell you.
If you are concerned with your children seeing you as a housewife (a term that I loath, and resent when my dh puts that as my employment on our taxes) ask you dh to do the occasional load of laundry, and to cook once or twice a week. I do think that it would set a good example, especially for your son. Besides, raising your children is job enough WITHOUT all the housework. My dh is great about pitching in around the house. There is nothing that I can't do that he can't do nearly as well (okay, except cleaning the bathrooms
) He actually prefers to do the laundry.
My mom stayed home with us and "did it all" so to speak. When we started school she took on a number of jobs over the years that allowed her to be with us when we got home from school, or very nearly thereafter. All my opinions of her "sacrifices" for us are positive. I am glad that I had such a great roll model who enjoyed her responsibilities of raising her children. It is probably because of her that I stay home with my own children.
Someday I will re-enter the working world (do I have to???) and there will be plenty of time for my kids to see me as the wonderful, responsible working mother. Of course, teaching will allow me to keep hours somewhat like my kids and to still be there for them.
Cut yourself some slack. You have the best job in the world.