Well actually Groundbum....
Nine times out of ten the computer does not know the childrens ages. Can you remember the last time you booked a ticket and were asked your age??? I cant. I have been asked for my date of birth for my APIS entry but that is not associated with the booking process and therefore not linked.
Airlines in the past used to assign seats based on group bookings (if you booked as two or more passengers then generally if available the seats would automatically be assigned together) but this led to problems in that perfect strangers could be seated next to one another if they were booked as part of a large group etc etc.
Now with a general industry wide cut on costs this has changed and airlines now only provide seat assignments on a limited basis. Hence BA only allow you to select your seat 24hours in advance if you check in online (unless you are a FF) and obviously BMI are now doing something similar.
Facilities with most airlines do exist to allow you to get seats together so why not use them instead of coming online and complaining about it? I appreciate Alex's problem and I can imagine it is very stressful (is it obvious I am not a parent???) however she also admits that she pays for the cheapest ticket and therefore...the old saying "You get what you pay for" etc etc. Now if she had said she paid the highest fare I certainly would be saying something different.
Perhaps BMI should adopt a similar scheme as Aer Lingus have where you have to pay per seat for an assignment!
But as for a computer being designed to work around this kind of thing? Well computers are not "intelligent" yet, they are unable to make those kind of assumptions. Indeed all it takes is for someone to design one that does but this has not happened yet!!! And this is exactly what I said in my previous post which Groundbum had difficulty understanding despite restating exactly what I said about complexities only in a different way!!!!