I would say the team actually has a pretty good chance. In one comic Thor funneled his immortal energies through mjolnir and directed that energy at Galactus causing Galactus to flee and remark "If I do not flee...then I shall surely perish!" I would say that the other members of the team can do at least enough damage to weaken Galactus to the point that a god force blast from Thor would effect him as it did then.
Team wins. Just too much firepower. Big G goes down.
Not sure why Odin is here, but if you want to go that route, Shazam couldn't beat BA and had to BFR him. Captain Atom creates Nuclear explosions on contact, Thor can get a big cheap shot in with his hammer that does almost as much damage as Odin's headbutt. Then you have Photon and Superman blue, I am sure they can drain him while he is trying to regain his consciousness. I like Big G but this is too much for him; However if he ends up beating the Celestials (which i hope) I'll give it to him.