Can i file as head of household? Can i claim my girlfriend and her child?

MY child, my girlfriend and HER child all live with me 365 and i support them (girlfriend has no income). Can i file for head of household and are there any benefits to filing head of household? Can i claim my girlfriend and her child on my return and again is there any real benefit doing so? Please dont take me asking if there is a benefit to it the wrong way.. Is it worth the extra time and paper work todo so or maybe not? Thanks in advance!!