My Costco membership is up for renewal, and it reminds me to suggest this great cost-saving tip to you: split a membership with another person--maybe a mom like yourself. So far, I've shared my membership with five different people--a mix of sexes--and Costco never blinks. I just come into Costco with the other person, they get their picture on a new card, and pay me the $22 or so. I've found Costco to be worth it on most items (be sure to compare!), and especially on large furniture items and electronics. I got my mattress set from them for maybe half of what I was looking to pay at a mattress store--name brand and high quality. I buy all my electronics from them (and save the boxes)--when my DVD player died after a year or 2, I returned it for full price and bought a new one. No questions asked. (Note that they limit the return time to 6 months on computers.)
I consistently buy dog food and treats, toilet paper, paper towels, bottled water, cheese, butter (did you know it freezes beautifully?), lunchmeat, eggs, some produce (it is a lot for a mom-and-kid family!), printer cartridges, batteries, bathing suits, tomato sauce, and Gatorade from them. You have to go often enough for it to be worth it, but for us, it's a win-win.