along the same lines as those suggesting adding up ALL expenses to figure out a workable budget-we did that for the regular monthly expenses and got a figure, then we took EVERY non monthly expense we could think of (actually looked through our check registry for a prior year to get an idea) added them together and divided by 12 to get a number for that to include in our budget. we include-homeowners (or renters) insurance which is only paid once or twice per year, car insurance (we pay bi-annually to save $5-$10 per month that the insurance company charges for monthly payments), car registrations, average number of oil changes per year, property taxes (we pay ourselves vs. escrow account), propane, vet visits, and a couple of services we use (pest, weed abatement), and when my kids were younger it included summer camp (daycare) fees as well as an estimate for school clothes (my kids may be the exception but their consumption of new clothing went WAY DOWN as they got to the point of no longer outgrowing stuff). every month the amount for the non monthly expenses gets auto transferred from our checking into a separate savings account we call 'reserve'. if we have one of those expenses during a given month I just transfer into checking the amount I need for that payment. when we were paid bi-weekly we had 50% of the monthly amount transfer in with every check.
I've also found that it helps budget wise if I have yet another account set up that holds the money I budget out for gifts/holidays over the course of a year-these would include Christmas, everyone's birthday (and when the kids were younger and got invited to birthday parties an amount for those gifts), valentines (small amount for the cards the kids gave when younger, candies), easter (those dang baskets and contents add up), and Halloween (candy and a minimal amount for costumes). again-we divided the estimated amount by 12 and it gets auto transferred into that account each month. this way our budget doesn't take a big hit when this stuff rolls around.
if you try doing this on paper you may be initially shocked

at how "little" money you end up with in your day to day spending budget BUT when you consider that the amount you are left with no longer has to be stretched to cover everything you're going to be setting aside for it can seem like a much more manageable amount. I also agree with tracking every expense for a couple of months and to try using cash for some day to day expenses-we've been doing both for the last 2 months and it's eye opening when you start seeing on paper how much the occasional starbucks, fast food, or convenience food (for us that's buying frozen stuff that I can make for a fraction of the cost and freeze for quick cooking myself) adds up. it's also more "real" to see the amount of cash declining in your wallet vs. just handing over a debit card.
p.s. don't know how old your kiddos are, but when ours got around 5 or so we set a monthly budget amount for 'family fun' and told the kids what the amount was and how they had to help decide how to spend it. if they wanted to go see a movie in a given month we looked to how much we had left in the fun budget and how much it would cost to see if we could afford it-and they got pretty good at picking and choosing once they got the hang of what stuff cost (and it was interesting hearing them discuss a potential outing and decide if they wanted to put it off in favor of rolling the budgeted money over to the next month to do a more expensive activity).