Hi, Welcome Aboard, sailingnate,
We've met cruisers on 20 ft. boats with one kid aboard, born during their travels, so I think age is not relevant. Parents' vigilance is.
gets pretty cold in winter, though not to MN standards, and much of your beginning sailing will probably be in spring through fall. IMO, start with a small trailer-sailer, and trust yourselves to know when it's time to move up. There's plenty to learn to keep you busy. It's different from driving an SUV. There's heaps of rules of the road, and those sorts of technicalities, and then there's learning
how to use your boat to its best. Starting small limits your risk, and may actually make it more fun. Wow, you'll sure know a whole lot by the time you retire, if you pay attention! :-)
My two cents.