not so at all
ref apaddyinuk saying it's not at all possible for the computer to do this. Quite wrong!
A computer will do whatever it's told, and can do anything you want it to do. I could make a computer that poured nice cups of tea whilst dancing the can-can!
The reason computers do not do all that you want them to do is that nobody wants to pay for it, ie commercial reasons!
now obviously the BMI computer knows it has a reservation for 2 adults and 2 children aged 4 and 7. So somebody at BMI can sit there and write a rule for the computer that says they should try and sit this group together, or the rule that every children must be near an adult member of the group, ie 1 adult to 3 children or whatever, etc etc.
Why hasn't BMI spent the couple of thousand quid this would cost sorting this? Maybe because everytime you change something on a computer you run a good chance of breaking something else. Maybe they have so few bookings like this it's not cost effective. Maybe it's because they do want you to pay for more expensive seats where this is doable. Maybe they want to discourage young families cos they don't make money on them. etc etc.
but I bet somebody somewhere has done a cost/benefit analysis and decided it's not important enough to get done. Kinda like my DIY list! I know all the broken things at home, it's a matter of them getting to the top of the to-do list. Same with big computer programs.