The answer I'm giving you is one based on what's known as "generally accepted accounting principles" (and specifically for any other accounting geeks out there, Statements of Financial Accounting Standards #116 and #117).
I think you do need to put that notice in the paper--it's a cheap and reasonable way to CYA. If you solicited donations specifically for a track, and your donors respond to that request, you're obligated to use it for a track unless they tell you otherwise. (I disagree with Critter here--I think that is, in effect, a contract.) Such donations are termed "donor-restricted." According to this one manual I have on non-profit accounting, "if an organization accepts resources expecting that it can comply with donor restrictions and later finds that it will not be able to meet these restriction, it must either return the resources to the donor or reach agreement with the donor to have restrictions removed or changed."
As for the comment about parents whose kids aren't there anymore not having a say in how the money is used--it's entirely possible that some of that money didn't come from parents to begin with. Maybe you solicited local companies for donations?
But you might have another "out" here. There's a difference between this kind of donor restriction discussed above, and a situation where your Board imposes a restriction. Let's say that instead what happened is that your Board made a decision (for example) to set aside 10% of your receipts each year to be used for a track. Since the Board at that time made that decision, the current Board can change that restriction with a Board resolution/vote--it doesn't matter that the same Board people aren't there.
Practically speaking, though, if you are dealing with donor restricted funds and you can't track down the original donors, and your legal notice doesn't get you anywhere, I think it's very reasonable for your Board to elect to use the funds for other fitness related items. Your liability would be limited to having the donors who gave money for the track come back to you and say they want their money back because you didn't use the money for what they intended. The chances of that happening are probably very slim, and you would be able to show a good-faith effort to reach the donors by putting the legal notice in the paper.
Finally, if you're big enough to be filing form 990 with the IRS, check Part IV--Balance Sheets and see if you have anything in the "temporarily restricted" or "permanently restricted" lines. If these truly were donor restricted donations, the $14,000 should be showing up in there. If it's not, there's the possibility that someone has already looked at the materials used to solicit the donations and determined that they really weren't limited to the track. Or, someone may just have done the tax return incorrectly....
