What a dusty predicament.
1) She's going to spend it how she see's fit, so long as your childs looked after well, who cares.
2) If you're worried about the inequality, buy your own kid stuff in addition to the maintenance (no law against it), maybe it'll force the others to hot up their own fathers (if they're in the picture).
3) Really need to get to the point where something this dusty isn't considered an issue for just black people. Tilbury is evidence that this sort of behaviour isn't exclusive to blacks.