Re: Lessons you have learnt from other weddings...
cinammon_waffle... how about having pails with coloring books and crayons at each table where you know there will be kids? i know here you can get those from the dollar store too, i'm sure there's an equivalent somewhere in the UK like that.
at the very least, it'll keep them occupied and hopefully in their seats, next to their mums. i know it sounds hopeless, but often times, kids are running around at weddings because they're so bored and there's nothing else to do to relieve them of their high energy!