My dad took the Buick to a local mechanic. He confirmed that it definitely was the window assemblies, and not an electrical issue. They all broke at once because GM window assemblies are pieces of shit. And, you can't just buy the little piece of the assmbley that broke - you have to buy an entire new one. If you buy it straight from GM, it costs around $300 each. I found them online for around $200 each. The mechanic, however, found them for $100 from a junk yard or a wholesaler or something. YAYS. I told dad that I'd rather just leave the duct tape on, but he wants them replaced, so he got an appointment for Friday morning. Woo.
Also, an FYI, if your windows don't work, your car won't pass inspection. Fun stuff.