Need advice with a complicated scenario

[KingMerv00]

The PC's:

Dread Necromancer 7 (Accompanied by two hag skeletons)
Illusionist 5/ Master Illusionist 2
Sorcerer 7
Cleric of Pelor 7
Rogue 4/Swashbuckler 3
Ranger 3/Rogue 2/Paladin 1 (Aasimar)

The PC's were hired to bodyguard an important public figure named Finwe Splitskull on the trip to a major peace summit. (Yes, I stole the name Finwe from Tolkein.) Finwe was chosen as the moderator between the elven and dwarven kingdoms because he is the world's only half-elf, half-dwarf, loved by the people of both nations. and has vast connections in both societies.

The PC's successfully protected Finwe from some disorganized attempts on his life and got him safely to the summit. The summit was to be held in a special bunker in a demilitarized zone between the two nations. The entire bunker is cloaked in a anti-magic field to prevent magical attacks and enchantments. On the summit grounds we have the following people:

1) Finwe (A fighter 4/wizard 5/eldritch knight 1)
2) The Queen of the Elves (A high level wizard)
3) The King of the Dwarves (A high level fighter)
4) 4 servants (One of which is an evil Fighter/Rogue/Assassin)
5) 3 shield guardians (one protecting each of #1-3)
6) A legendary minotaur acts as the sole security guard. (Both sides agreed it was best to keep the armed presence to a bare minimum for safety reasons).
7) 3 airships and their crews (parked about 1000 ft from the bunker)
8) A groundskeeper (An evil Sorcerer working with the other assassin)

Long story short, Finwe is evil and is working with the assassins. He used his military connections to engineer a coup while the king and queen bicker in the bunker. An army from each side is currently riding towards the summit with the intent to secure the area and take the King and Queen alive to make Finwe's ascension to king appear more legit.

The PC's did some investigating and discovered that the armies are arriving in an hour or so but don't know who is responsible. Last session ended with them standing just outside the bunker speaking through the open door to Finwe, the Queen, and the King regarding this new information. The assassin servant, seeing the plan falling apart, secretly drew a shank and leapt towards the king (assassin death strike). The party paladin rolled high in his spot check and will maybe have a chance to stop the assaassin in his surprise round. The groundskeeper is also standing outside ready to cast wall of stone to seal the bunker though the party doesn't know that yet.

The only way out is by airship. Long distance teleportation can't be used for reasons unrelated to the assassination plot.

As you can see, this is complicated. I haven't settled on character levels for the assassins or the queen/king. If I set them too high, the PC's will feel like they are watching a cut scene they can't control. If I set them too low, they'll kill all the bad guys too easily and kill the drama involved. Any advice?

Also, I'd like extra advice on how to make this scenario more interesting from a story and battle tactic POV.

[Aidan305]

Firstly, have the armies actually started the coup yet? Or is taking the King and Queen the first step?

Secondly, if it's a political game, the players will most likely have expected an assassin, and will probably expect more. Have the assassin die reasonably quickly so as not to bog down what will be a fairly intense scene anyway.

Have Finwe suggest that the group leave, staying together for their mutual safety. The lives of the King and Queen are paramount here after all.

Cue the wall of stone.

That should set up a decent amount of panic, and then it's time for the PCs to be PCs.

What's the legendary minotaur equipped with? Might I suggest an adamantine greataxe of some sort. That combined with the minotaur's strength should allow the group to escape if the PCs think of it and if the minotaur's strength on its own isn't enough.

Next up, you've got to choose the airship. The Elven queen will demand that they go on her ship, while the Dwarven king will be equally adamant that they go on his. Bickering squabbling and negotiation on the part of the PCs should take place here with Finwe acting to attempt to stall things as long as possible without revealing himself, have the sorcerer interrupt the proceedings with a whole host of summoned creatures to act against the PCs.

Eventually, the party will have to force a decision on the King and Queen, which will most likely be that the group use the PCs airship (I assume that the third ship belongs to them, correct?

The PCs escape in the nick of time and breathe a sigh of relief as they fly away over the heads of the two advancing armies.

In the night, Finwe, the King, and the Queen all disappear. (Finwe's offed the two of them/disabled them and has run off to rule his new empire.)

With luck, you've have some very annoyed PCs who will be itching to have a go at their new Big Bad.