Being frugal is much easier if it is a family affair. Children and spouses can wreck havoc on your budget if they don't realize what it is you are trying to accomplish! Another reason to involve them is that truly, you are setting the standard for your children when it comes to financial dealings. I learned my frugality from my mother... and my kids will learn my habits too. It is a chain which can either be valuable, or detrimental!
So how can you get the family involved?
When my kids were very little, something they found quite amusing was to sit with me at home and look at the grocery store sale brochures and watch me cut coupons. They would point out items they liked, and I would tell them whether it was a good sale or not and we would talk ahead of time about whether we would be picking some of that item up on our shopping trip. This way they already knew what we were going to the store for, and it became more of a fun game rather than a chore.
In each store that we visited, I showed them the sale tags and pointed out what color they were. It was a rule that they were never to ask for anything that wasn't on sale. :) This took me all of two minutes to do, but eliminated a lot of pleading. Sometimes they would point out something with a tag and I would say, "hmmmm... that's not a very good sale", but now and then I would surprise them with a "you know what? That IS a good sale, we can get one of those."
There is nothing more deadly to your budget than buying items that your kids are whining for. It completely defeats the purpose when you end up buying full price, expensive items.
As your kids get older, so does their comprehension of what you are doing. One idea that I heard once was to have the kids help with finding sales and cutting coupons, then after you had done your shopping, you add up your savings and put that money aside for something your family wants. Maybe it is a vacation somewhere! Maybe it is a new game system. Whatever gets them motivated. You can choose whether you put aside the full value of the saved money, or just the value of the coupons... the second option means you are saving on your budget, but also saving for something fun. Most store receipts will give you both totals.
Kids aren't the only ones who can destroy a budget at the drop of a hat. Spouses can be even worse! To get my husband involved and informed, occasionally I would send him to the store with a VERY short list and a couple of coupons so that he could personally see how much it saves to shop wisely.
I also ALWAYS used to show him my receipts from my shopping trips showing the original amount of the groceries, the amount saved, and how much I paid. (Rarely was the amount saved less than the amount paid.) Can I tell you that you will be surprised how excited your husband can become when you are saving your families hard earned money! :)
Spouses pick up very quickly on what is a good sale and there have been many times through our marriage that he has noticed something excellent that I didn't know about.
After sixteen years of marriage, I can honestly say that Mike & I have never once fought over money. We have joked with each other and contemplated that the reason for that might be that we have never had much to argue over, :) but we both know that it is because of our respect for our earnings and a joint desire to live the best we can with what we have. It eliminates a lot of selfishness when you live frugally.