Lil Eazy -- son of Eazy-E -- is so ecstatic about his dad's hologram debuting on stage with Bone Thugs-N-Harmony, he's planning a massive party to celebrate it ... and to mark a milestone.

Lil Eazy tells TMZ he will definitely be there when hologram Eazy-E hits the stage at the Rock the Bells festival on September 7 -- because that would have been his father's 50th birthday.

LE says, "I am happy my father gets to get honored ... it's exciting" -- and he's going to keep it rolling after the concert by putting together an over-the-top afterparty.

As for whether Lil E will be on stage with BT&H and Holo Eazy-E -- nothing's been announced yet ... but they've collaborated several times ... including the 2008 "This Ain't a Game" video.

***Warning: Explicit lyrics***