Interesting question. Lacking any specific prohibition in your bylaws, I'm guessing you probably could. But that's not the type of thing I would want to do without a formal investment policy in place. Generally speaking, shares of stock are for long term investment, which I don't think makes them appropriate for your typical PTO. I'd be pretty ticked if I gave money to the PTO to buy playground equipment, only to find they invested it in the next Enron.
