Seeking ideas for an assault on Mt. Olympus

Since the holidays I have been delaying the closing arc to the ancient Greek themed Dnd campaign I've been running, hoping inspiration would strike. But due to burnout or just lack of ideas, I'm really hoping folks can help spark some inspiration.

The campaign takes place in ancient Greek times, all around the Mediterranean, with of course plenty of relevant dnd monsters added in. Doused in Titan-blood as they escaped Hades earlier in the campaign, the PC's have the power to slay deities, and as the campaign has progressed it has taken on a God of War bent, with them allying with some gods and battling others. They slew Aphrodite and the Egyptian god Set she was manipulating, and befriended the rest of the Egyptian pantheon and many forest gods of Gaul. In defiance of Poseidon, they raised Atlantis back above sea level, and its aquatic adapted denizens are grateful. They even have tenuous control of a 6 headed Hydra, and were hoping to ride it into battle before it's inevitably laid low.

Now the time has finally come for a large assault on Olympus, an epic sized and divinely protected mountain but still a location on earth, not another plane. The chief Olympian gods that have become the campaign 'big bads' are Zeus, Ares and Poseidon, though others can assist. Hermes has been hinted as a potential ally to the party, giving them indirect aid previously.

The group are 6 lvl 13 PC's, but as this is a one off special mythological setting, that is plenty high enough level to battle the Gods as I've statted them to provide appropriate challenge for the party. Rather than help with stats, I'm hoping for any ideas that people may have for interesting encounters, combat or non-combat related, while progressing up the mountain (I'll probably say Zeus can smite any direct airborne assaults so they need to work their way up, turning it into more of a dungeon in a sense). They have godly allies, but I'll probably have them get separated from them.. only having them reappear so they can magically grant the group a long rest perhaps?

How would you run Mt. Olympus as a worthy campaign-ending adventure? Apologies if rambling above, just hoping for any ideas from the community, big or small. If you have any questions or thoughts, let me know. Thanks!