You want a guaranteed A pass every time? Just travel with kids. No matter how late they show up, they still get that early pre-A boarding slot (at least when I've seen).

I understand the issues involved, but it doesn't seem fair when the A group people were careful to show up early and get trumped by the last minute people with kids. If you want to give them something, bump them up one boarding group from that they show up for. Even at the last minute, being up one group should allow them to find some seats together (though not necessarily 4 or 5).

If we're going for complete equality and fairness in the boarding process, then it seems that it should be applied to all, not just among those traveling without children.