I really dislike the word 'kid' in relation to a child. It just doesn't sound right - well, at least to me!
We have two daughters and they have always been 'the girls', so that was easy.
Their children, one of each variety, are our 'grand-sproglets'. I am not too sure how this came about but it has stuck and they are perfectly happy when I call them to heel by yelling 'sproglets!' and come happily trotting over, knowing there are no other children in the vicinity that they could be confused with. It works well!!