Getting divorced is a financial blow to any family. Even in the best of circumstances there are double the housing expenses because suddenly there are two homes to support, two phone bills, two cable bills, two water bills, and so on. When there are kids involved and split-family living becomes the lifestyle of choice for the foreseeable future, finances can get even stickier.
If you are on reasonable terms with your ex-spouse, there are ways to avoid common pitfalls of supporting your kids financially. If you are not, there are still limited actions you can take without having to involve the family lawyer, they just may not be as equitable.
Don't use money as a manipulator. The children will be the only ones to suffer. If you have an agreeable divorce, consider consulting a financial planner together to set up the best situation possible for your kids. If your divorce is messy, talk to someone about setting up a trust where a neutral party has control from the very beginning.
Agree on how to handle day-to-day expenses. Who is going to write the check for swim team? How will shopping for birthdays and other holidays be done? Will you each contribute a certain amount? Who will buy the kids' clothes? Will there be a primary party responsible for the kids' expenses or will you divide costs based on activity (such as one parent handles medical expenses, the other handles childcare)?
Establish a savings account for each child. Agree to a set amount that you will each contribute regularly (monthly is ideal). That money will be available for unexpected expenses such as cheerleading camp or a band trip abroad. When those events come up, you'll be able to deduct the amount from the savings account—with no arguing or financial distress on either party.
Depending on how you set it up, this same account can pay for swim lessons, braces, football practice, and other day-to-day expenses.