M.: You’re wasting a perfectly good fight because it’s just an expense.
What you spend is either a cash gift or a loan, but it is something you spend, whether you charge for the project and pay cash for “elsewhere” or charge “elsewhere” and pay cash for the project. This is especially appropriate if the “other projects” are, as you say, projects, not trips, debt repayments, or anything else. Whether you’re using a freebie or credit for the bathroom or bedroom, there’s a microscopic haircut.
And if “elsewhere” involves more pressing things that require money, then please don’t pressure your wife into turning down a chance at better financial health just to keep a gratitudinal purity with your parents. “Thank you, Mom and Dad, for helping us finish the bedroom. You are the best”, this would be true regardless of what kind of money you spent, where and in what order. Assuming they are in fact the best.
If your parents are tying tight strings to their gift money and that’s why you’re now entrenched against your wife, making their pressure her problem, then they’re actually not the best. And you choose the wrong side. Rather, you should support your wife and stand up to your parents for your right to manage your household finances as you see fit, and assure them, for the sake of appeasement if you wish, that even if you have other priorities for the money, their generous donation will take the girl’s room to the next level, which, again: a huge help. Thanks a lot. And you should categorically refuse the gift if they are angry with you for your candor.
Unless your priorities stink and your daughter is in a plywood room while you embezzle funds to re-tile the hot tub. In this case, ask your parents to write, thank you very much. If there’s a financial constraint here and all the “gift this” and “credit that” is an anxious party game and your parents are really trying to help you and their help may be a bit far from brand, so just talk to them about what you need and intend to do and see if they’re open to it. Better to keep your emotional investment in your marriage as low-risk as possible and play around with “annuities” a bit.
What you cannot do, decently, is accept the money on the pretext of finishing the room when you have no intention of finishing the room in the near or mid future. A gift is yours, always and fully, to use as you wish, but pretense is a coward’s scourge.
Finally: Credit cards are more expensive and riskier money, so only charge “projects” if you need to or have plans and means to do so strategically, to pay off quickly and with little or no of interest. Otherwise, wait, if you can. Michelle Singletary didn’t make me write that. If I missed an “if”, well, damn it. But please let me know.