Ditto...the door lock cylinder is designed for not only electronic actuation with the buttons on the remote & when the key is inserted into the lock cylinder & turned to a
45° angle...but when the key is inserted into the lock cylinder & turned to a
90° angle...as stated in the owners manual (which is probably locked inside your glove box) you can MANUALLY lock/unlock the door when there's electrical failure.
So instead of "disbelief by parents with kids"...remembering that BMW did design a second way of access to things that can fail electronically...that even includes the tailgate which doesn't have a lock cylinder when there's electrical failure. It, too can still be manually opened...and those instructions are also in the owners manual.
The pic below is of an e38/e39 door handle...but the lock positions are the same for all BMWs for more than the last 20 years: