I'd pay off my mortgage, remodel the house a little bit to make it more usable, and look around for a reasonable lightly used car to replace my wife's aging vehicle. Then I'd help my siblings (and my wife's) out by paying off mortgages, school debt, and the like. I'd set up some sort of financial structure to make sure that my wife and, should they come along, my children would live without financial stress for the rest of their lives after I pass away. And a goodly chunk right off the top would go to my church and another religious organization that was very important in my life.
After that, I'd take up a bit of travel. I'd take lots of guitar lessons and buy more music equipment than someone of my skills can reasonably justify. I'd set up an endowed foundation to perpetually help fund the type of charities and other organizations that I think need supporting. And maybe get back to taking dance lessons regularly. I'd go to more concerts, and pay for better seats and the occasional meet-and-greet. And I'd spend time developing an open-source project idea that I've had for several years. And I'd probably pay someone else to mow the lawn, tend to the flower garden, and clear the driveway of snow.