What would you suggest?
Wait them out? They wouldnt accept food to be brought in, starvation is a HORRIBLE way to die.
Negotiate? Why would you want to negotiate with cowards who go after children of all people? It only teaches them that they can do that anytime they want and will get whatever they want.
Gas it? We all know what happened during the Opera, and these little kids would die MUCH faster than the adult capturs.
There's nothing they could have done but storm the place.