If I were you, I would do the same. Once a buyer shows interest in that old car, it’s better to get rid of it instead of spending more time looking for a new one. Driving that beaten-up car on a long trip is risky anyway. You can always get to your mother-in-law by other means, like buses, trains, or flights. Of course, taking a car is also an option. You can check where to rent a car for a travel to Boston here: https://buffalonews.com/exclusive/article_86aa387a-e106-55d0-a980-0b0a1b50db05.html . The site also has suggestions for scenic stops along the way where you can grab a coffee.
