If it's in a mutual fund then it's already invested.
I'm not clear as to whether you're working for a salary right now or not. If you are, then you could transfer part of that money ($5500) to a Roth IRA for this year, which would mean that it grows tax-free. Then on the first of the year you could contribute another $5500 for 2014's Roth IRA, which would shelter $11,000 of it. And so on.
I personally wouldn't withdraw that money and use it to pay down your $15,000 debt unless you were very sure you had the strength, frugality, and cashflow to contribute a substantial sum every month to build that $40,000 up again. You say your overspending has ended, but can you be sure? Presumably you thought that before, but then you built up $15,000 in debt. I would be very cautious about assuming that you're going to live frugally, but then not, in which case you'd just be cashing in that $40,000 and having it slip through your fingers, only to end up in the same debt-ridden spot.
Also -- as I understand it, you and your husband have both been running up the debt. It doesn't sound as if he's been living frugally and packing his banana to lunch every day and trying to make homemade meals while you're insisting on the Starbucks lattes and the fancy meals out every night. It sounds as if you're in this together. Someone gave you some money when you were a toddler, to save for some future purpose. I doubt they gave it to you to spend on luxuries and to bail your husband out of his habit of spending on luxuries. I think what would be appropriate would be if he cut back and lived thriftily until he can pay his $7500 of the credit card debt, and you do your part in budgeting and cutting back until you've helped save $7500 toward your part of the credit card debt, and you leave the $40,000 out of it. That's my vote.