Since it means a space to fill all of the parents are going to be effected. I would personally let the parent of the child that was injured know how you have handled the situation saying again you are sorry it happened and that you have terminated care for the offending child in the interest of safety of the group or something to that effect. As far as everyone in general goes I would just tell them that XXX is no longer going to be coming to your daycare. That is all of the info they need. Then let everyone know you have a spot because word of mouth from current families is the best way to fill a space quickly.