Create a family budget vision. Talk to your spouse and children about whatever budgetary constraints you are facing, or whatever financial goals you intend to set. By being completely honest about the bills and loans you have to pay, or your intention to save a certain amount of money for a family emergency fund (or a college fund, for that matter), you can help your family understand better your collective financial situation. This will allow them to change their perspective on purchases they make, and will help you make sure that whatever money crunching strategies you utilize wont be counteracted by a subsequent spree by your teen.
Another good technique is to create a list of usual expenditures per member of your family. Together, identify which items you can do away with in order to save up some extra money from your monthly income. By doing this altogether, you are making your family participate better and see the contributions they can make into making your familys finances better.