I'm one of those affected by the current proposal, so my initial reaction was to vote "Leave it as is". However seeing as we're all in this together*, I voted for "change plans to a fairer system".
I haven't thought about it in any detail, but one of the things the government did in Ireland to encourage population growth was to increase the amount of child benefit available for each subsequent child. For example, your first child you got £x per month, next child got £x + £y per month, third child got £x + £y + £z and so on. I'm thinking maybe doing this in reverse could be a good way to go - so, increasing the amount you currently get for your first child, and significantly lowering it for each subsequent child, to the point where it's zero for, say, the fourth and subsequent children.
This would have the benefit of discouraging the sector of society who pops out children in order to live off benefits, while not impacting too heavily on anyone sensible who chooses to have the nuraber of children they can afford. I have no idea if the maths behind this would work, it's just a thought.
I don't think CB should be scrapped completely, as it's a mark of a society that cares about all its merabers.
*sort of - I'm willing to pay my way, at least