It seem like you don't like Young Justice
Round 1: Young Justice doesn't have enough feat yet to face Cell & Buu.Too much power to handle, Cell & Buu win
Round 2: Meghan (Miss Martian) is a powerful telepath who can disable people with psychic attacks, and make them see whatever she wants. I think she's Young Justice hope in this battle. If they don't get blitzed first, Superboy and Cassie can distract them long enough for her to stall Cell and even neutralize him (She has been on par with DC most powerful telepaths before when she let out the white martian in her). However during the Babibi/Dabura story arc, Buu has demonstrated that he could fight through mental suggestion. so I'm not sure which way it could go.
Raven could imprison buu in her soul-self just for a few min cause Buu has showed that he could escape from dimension imprisonment before. They can all focus on the incapacitated Cell while Buu fight his way back
Best case scenario, they can take out cell while he's mentally down, but Buu can't be contain for very long, They all attack, but DBZ characters have a higher energy projection ratio so I can see Beast Boy, robin and Cyborg dying first. Superboy, Raven, Miss Martian and Impulse can last a while but Buu durability is too much to handle. Also Superboy doesn't have his TK (Tactile telekinesis) on Young Justice, and with Robin & Cyborg dead, they would be less coordinated and less efficient as a team....so they get stomped....Cell and Buu win
Raven could just summon them to the Phantom Zone or to the Dark dimension where it would take them months to years to find their way back no matter how powerful they are ( they may be planet busters but Ki/spirit force doesn't always have an effect on celestial realms). Young Justice takes this
(If no BFR, Cell & Buu win everything.)