[Gilgorm]

640i GTs are very scarce. With only 2018 and 2019 models, the odds of finding one are slim but the prices are usually very low for the type of car and equipment you can get.
The car is still made in Germany in 2021 for other markets so parts should be available. Unfortunately, this particular website is low on commentators.
The car is very large and the adjustable back seat is very roomy. Car seats are not a problem. A stroller? Easy peasy.
The trunk is the largest I've ever owned, a 6 foot ladder is easy with the seats down. I believe an X5 trunk tray fits with lots of room. I had to get some warranty work done on mine and the 2021 3 series and 2 series loaners were barely OK but nothing can touch the ride in the GT. This is a luxury car.
In all Canadian cars, they came equipped with the 2 axle air suspension which is off the 5 series European wagon rear end and the 7 series front end. Even in Sport, the car ride is exceptional. Most Canadian cars come fully equipped. I love the ACC with Stop and Go, interior trim (Nappa and Piano blk).
There are multiple reviews on-line. After checking them out, try and find one and take it for a test drive. You won't regret it.
Sadly, actual sales tell the story--Americans don't like hatchbacks so the car was discontinued in all of N. America.
Good Luck.