I ran in there for giggles, with only boone as companion. both of us were armed with anti-materiel rifles, and we slaughtered the whole lot of them. then we went down into the shack in the back of the fort and did what we had to do.
wich is to activate an army of securitron droids. lol. later on you can become commander of this army if you choose the yes-man questline. the ending is pretty abrupt and boring btw. a bigger-all-out battle would have been fun.
killing ceasar has no real effect at all. people just start saying "I wish I could have been there." or "wow you killed ceasar" etc.