I use a method similar to JJs, except I keep an excel spreadsheet for the entire year. Across the top are the dates we get paid (every 2 weeks). The first two rows are for our net pay, with the third row being the total pay for both of us. Then come all the bills, with description, normal due date, normal or estimated amount, and also if it's an EFT/autopay. I enter this number all the way across for the entire year, in the column that corresponds mostly closely to the due date. Plus I have simple formulas to add things up. As I pay something, I highlight that cell. Then I can tell at a glance if I forgot to pay something. Before excel, I used a handwritten list for years, and this has saved my bacon MANY times!
My DD found out the hard way how expensive it can be to lose track of a bill. She forgot to pay a credit card bill on time, and her interest rate went from something like 7% to around 25%.
On the subject of your children, it is so true that they grow up SO fast, and you will wonder where the years went. Everyone always says "enjoy them now"... which is such good advice.