Azizi
I agree with you about children not knowing or caring about the meaning of words - however, I believe the terms under discussion do not originate with children but are adult inventions which are calculated to mock and debase people of different colour, religion, origin, appearence, accent etc. Left unchecked, I believe they become ingrained in the child's attitude and so should not be ignored.
From what I know of collections of childrens rhymes and games, I have always thought that there is little of a racist nature apparent in the repertoire, but this may well be because of the influence of the collector, either as an imposing senior figure or as a conscious censor. Typical of this influence is to be found in the Opie's 'Lore And Language of Schoolchildren' where they state "Genuine erotic verse, however, is unusual. That there are villains among children, as among adult...... and from somewhere the ogre child aquires his strange salacious prescriptions, taking criminal pleasure in pressing them on juniors, and inscribing them on the walls of the school lavatory". Personally I'd be more worried about the Opies consorting with my children than an 'ogre child'.
I would be interested to hear how your research's progress.
A salutory lesson in recording children was related to me by a friend who was teaching drama around schools in London back in the seventies. He had spent some time recording children and had got a number of polite, somewhat genteel pieces. He threw a blanket over the open door of a walk-in cupboard and told the children he was going for a half hour break, but if they remembered anything in the meantime, would they go to the cupboard and recite or sing it into the tape recorder which he had left running. He reaturned 20 minutes later to a magnificent tape full of bawdry, erotica and general impropriety.