My kids already have their inheritance in the form of an education.
I'm not earning to hand over money to my kids on my death. I'm earning on the theory that I might live to 100. I probably won't, in which case they will inherit if I do this right. I sure as hell don't want the government to take it just because I happened to die early...that would be a double punishment for me.
With a 100% inheritance tax, your plan to give to charity would be thwarted.