Also note that most (all?) of Delta's D1 seats contain an airbag built within the seat belt. I am not sure how they work or are regulated for children.
They are easily turned off. I'm fact by default they're off unless buckled. There's a magnet in the buckle portion that causes it to activate. If use an extension, there's no such magnet and it doesn't activate.
As for most D1 seats not allowing car seats, it's due to the fact they're angled. Not sure of reason on 767.