Well a week wouldn't be an accurate gage. My first years as a SAHM mom with all three in school (I homeshooled before that and did non-stop kids from birth before that) were last school year and now this one. Kids have been in school for a week this year.
Last year was no vacation because I finally started painting full time which I've been wanting to do my whole life, and painting's not relaxing, and then that was hindered because I needed to clear the house of 10 years of clutter because my life was chaos from all the years treading water home with kids.
I'm a single mom, so there is only me here to do ALL kid and house stuff after school and weekends, so my only "free time" is until 2:30 weekdays when I have to get ready to pick kids up after school....so the day flies by.
With the painting and decluttering all last school year I was very stressed for time and money. This year I'm just painting full time but it's STRESSFUL. I just killed myself to meet a deadline for a show yesterday. Sometimes I have paid commissions and sales, but mostly I'm building a body of work for future gallery representation which is not paid of course. So I'm busy and stressed for cash, and the kids get off the bus at 3pm.
On the opposite end of spectrum, I have working friends with NO kids who are very busy with work, but technically have evenings, weekends and vacations "free" from kid obligations. However, they are just as busy and burdened as anyone else if they have other goals and activities outside of work.
I know only a couple of SAHM moms who are totally lazy and watch TV, exercise, do their nails, and get organized every week like we all fantasize about. And the ones that do that have that sort of personality, have comfortable finances, or are opting out of the income they could get by working in exchange for "doing nothing". Likewise I know very few childless people who are relaxed and leisurely all the time when they're not at work..there are those types of people, but they're not the norm.
Also, don't forget, most SAHMs who don't work have chosen to live on a super lean budget in exchange for more time at home. This creates it's own challenges. I'm "free" to paint and do exercise DVDs and tackle some housework while kids are at school, but my working friend next door is "free" to buy all kinds of stuff we aren't including a housekeeper, fancy gym membership, and lots of high quality take-out food and meals in nice restaurants. I have to cook! Every damn day! And pack lunches. Every day. And clean the kitchen every night while guiding homework, baths etc...
Nothing is realistic for one week.
But sure, save up some dough and take a week off work while you're kids are in school. It will just feel like a week off work though.