If possible, establish a credit card that allows both parents to sign on it. When you need to pay for something immediately, this card allows you to do so without having to track down the other parent for half the funds. You could also do something similar with a joint checking account for your kids. Keep in mind this will only work if both parties are fiscally responsible.
Sign up for a prepay lunch account if your school has it. Prepay programs, such as Mealpay Plus, give notice if your child's lunch account is running low—so your child doesn't have to be home that night to notify you he is out of lunch money.
Start a college fund. This fund should be separate from the regular savings account and should not be touched as it is growing. Agree with your ex-spouse ahead of time of what the funds may be used for and how the money will be shared if your child doesn't attend college.
Buy life insurance. Even if you and your ex aren't on friendly terms, both parents should buy life insurance that will financially cover the remaining parent should one die. You can designate the money be put in a trust for your kids to be managed by whomever you choose, or have the money go directly to your ex-spouse. Work it through the same agent so the policy is similar on both sides.
Meet with a tax advisor. Often times you may claim Single/Head of Household if you have a dependent. It may be worth you splitting your dependents equally or sharing them by odd and even years.
Write a will. There is much more to a will than just who will take custody of the kids should you and your ex die. You both need to decide how you want your assets handled if you are not there to do it for the kids.