Elizaregina - reading the OP, it seems that the children weren't just standing on a booth, they were climbing on all the spare seats and booths, and sliding along the backs of the booths behind other diners - how is that not bad behaviour?
There's bound to be a bit of disruption from children in a family restaurant - I know that and accept it. But I don't think it is unreasonable to expect the parents to keep their children at or near their own table - or under it, as another poster described her child. But it is not reasonable for a parent to allow their child/ren to play all over the restaurant - it is a restaurant, not a playground, and different standards of behaviour do obtain there. And for me, there is a big difference between a certain level of noise and disruption from children at a nearby table, and the noise and disruption of those same children playing around my table.
From the OP, it also seems to me that it was more the attitude of the mums that irked the OP than the behaviour of the children. One mum did remove her child and mutter sorry, but then they all completely ignored what their children were doing, and apparently made no attempts whatsoever to stop them disrupting the whole restaurant and using it as a playground. Children are not always little angels and are going to misbehave/push the boundaries sometimes - it is how the parent deals with this that matters for me.
And I would like to ask the parents of children with SEN - would you completely ignore such behaviour from your child? I accept that you might well need to deal with your child differently because of their different needs and reactions, but would it be right to ignore the behaviour altogether? I do understand that having SEN might make a situation like a restaurant very challenging to cope with for both child and parent, and that understanding and tolerance is needed from other people, but how often is it the right reaction to do nothing at all, even when others are being disrupted?