I do feel strongly about this........ it should be expected that families sit together. let alone have to pay for "the privilege" - except perhaps if you have a large group with more than one immediate family.
BUT......We have had experience of scheduled airlines trying to split us up - both BA and Virgin!
This was in spite of calling in advance ( more than once) to ensure our seats were together, children's meals booked etc. before both journeys.
In fact, in '95, I stood my ground for 3 HOURS at Miami airport arguing with this woman who insisted that my FOUR YEAR OLD son and my 7 year old son would be fine on their own ... " You can visit them once the plane has taken off" AND "Nine hours isn't too long, especially if they sleep". [ I should add that they were expecting each of us - all four - to sit alone in different parts of the cabin!!!]
Welllllllllllll ............ Okay, now she had gone way too far with me, so with 20 minutes before take off, I insisted on seeing the top person ...... we got two together in Club Class and two together in what would have been Club if they'd had enough Club class to fill it....... yes..... they were sitting amongst empty seats in the front of the plane.