I just got married to a wonderful lady with two children. We've talked over our financial situation, and we're determined to get out of debt within two years. This will mean some big changes in our teenagers' lifestyles. How can we break this to them gently?
Having your wife, who is also their mother, on board with the plan makes a big difference. I think all of you need to sit down and have a frank, but loving, discussion about the changes that are going to come with this marriage for everyone. The kids have to adjust to a stepdad being on the scene, just like you have to adjust to a new marriage where teenagers are part of the package.
Let them know that you don't want to be the bad guy but that you and mom have been looking at the money situation, and things just don't add up. Then, it wouldn't be a bad idea for mom to speak up at this point. Let her tell the kids that you've both decided it's time you made the money behave, and this will mean some lifestyle changes for everyone.
Listen to reasonable input from them, and let them know their thoughts and feelings matter. But they also need to know things are going to be different, and this part needs to come from mom. Otherwise, they're likely to see you as the wicked stepdad.