My response might be a little harsh and definately won't win me any popularity points here - but here it goes.
No one balances it well. If they say they do, they are in denial or clueless. Being a parent is a full-time job plus some and doesn't leave a lot of room for anything else. Women are stretched to far and too thin nowadays and families don't devote a lot of time to each other anymore. We are overscheduled and running ourselves ragged. We are a fast-food, convienence food pop-it-in-the microwave go go go society.
Having said that, let me offer 1 suggestion. Kevin Lehman (author of "Making Children Mind Without Losing Yours") suggest that kids should only be allowed 1 outside the family activity per semester - which he even admits is hard - but necessary. He believes that families don't spend enough time together and that the quality time together far outweighs the missed activities in teaching children about life, love, and what's important.
I know that its probably impossible for you to leave your job and focus on your family as that is the case in most families today (another book here "The Two-Income Trap"), but remember that they are only young once and you only get one shot at raising them properly.
I love my job - I'm a teacher - but I had to make the choice to stay home and forgo my career for the time being. I know I'll go back to teaching, just when they are older. I was just missing too much, our lives were too hectic, and I was settling for something I didn't want. Are we financially better or worse off? Well, money is tight, but it was before too. We don't eat as much fast food or convienance food, our lives have so much less drama, and my children are better for it.
I am not condemning you for working - I know some of us do not have those choices to make, but paying a housekeeper? - that's paying someone to do my job! and what message does that send to my children? what lesson are they learning there?
Your situation is complicated by the fact that your children are of such varying ages! I can definately understand how schedules can easily become too full too fast. Best of luck to you and I hope that you can acheive a balance that works for you!