Zero. The number of acceptable dead children of any nation is zero.
Everyone on this board would feel that way, and almost everyone in the world would feel that way including the Israelis.
There is one group in partlicular that does not feel that way though, and that is Hamas.
Hamas would not have used Palestinian children as human shileds in order to attack Israeli civilians which included Israeli children if they were not aiming for dead children on both sides.
Unfortunately for their families, Hamas achieved their goal and got their wish of dead Palestinian children that they could use as political fodder to attack Israel with.
Most people would condem Hamas for that. You apparently have not.
I would hope that you would value the lives of Palestinian children and Israeli children more than to support a group that is actively trying to get as many of both groups killed for political ammunition as possible.
There is a way for the Palestinians to obtain more rights, there is a way for Palestinians to truly fight for freedom, but Hamas's tactics of terrorism and aggression towards people on both sides of this conflict couldn't be any farther from the powerful tools of peace needed for the Palestinians to really achieve true freedom.
These are true freedom fighters who are actually working for Palestinian rights and freedom:
http://www.seedsofpeace.org/
When you actually look at the goals and actions of Hamas, there is nothing that promotes the rights and freedom of the Palestinians:
Gaza Terrorists Resume Rocket Campaign Hamas says still seeks Israel's destruction