What happens if you meet, JG and go back and tell Caesar of him, or kill him and tell Caesar? Is there a dialogue option?
Or if you have WW and do this < is there anything.

Btw i'm asking this, cause I really don't like doing HH it bores, me, so instead of doing this myself, i'm wondering if anyone else has done this?

No, you can't inform Caesar about Graham's death, not even meeting, here's the explanation why:

http://www.formspring.me/JESawyer/q/210213371281171299

Thanks pal!

If you kill Caesar and tell Joshua, he gives a small talk about it.
If you kill Joshua, you are unable to tell Caesar about it.

Though Joshau does provide dialog as to why the Courier might elect NOT to tell Caesar about it, basically implying why the Courier chooses not to.