The destruction of the Ice Crown is a very easy Quest with more than one solution. You only really need Morkin and a few ancillary Lords. So your first descision is “What to do with Luxor and Co?”
Now, either send them on some errand wandering the land, recruiting men and fighting wars. Or just hide them…

Method One: Farflame the Dragonlord

Send Morkin and Rorthron the Wise North-Northwest through the Forest of Shadows, across te Plains of Orgrim and between the Moutains of Dodrak and Ashimar.
Send Rorthron into the Forest of Dodrak and then Enter the Mountains of Dodrak. At the North most point is a clearing in which you will find Farflame the Dragonlord. He will be at the Ruin of Coroth. You will get there about day four or five.
Keep sending Morkin North-Northwesterly and onto the Downs of Mirrow, passing Lake Mirrow on your way. (remember this you may need it one day)
Morkin is travelling into the Forest of Lothoril and up to the Keep of Lothoril where you will be able to recruit Lord Lothoril.
Farflame should just play catch up, something that is very easy for him to do.
After recruiting Lothoril use him to fight and destract any of Doomdarks armies that may be close at hand. There is oftern one hovering around here at this time.
Morkin travels North-Northeast to Weird Henge. Here you will find a Cup of Dreams allowing him one extra day of travel.
He then travels directly east over the Plains of the Lost, through the Cavern of Death and into the Moutains of Death.
Leaving the moutains southerly into the Forest of Doom you will find The Tower of Doom and here you will find the Ice Crown. With Farflame the Dragonlord here the destruction of the Ice Crown will be complete at the end of day nine.

Method Two: Fawkrin the Skulkrin

After entering the Downs of Mirrow send Morkin and Rorthron Northwesterly through the Downs of Mirrow, Passing Lake Mirrow and on to the Plains of the Moon
Fawkrin The Skulkrin is at Moon Henge – far west hand side.
Head Northeast through the Forest of Lothoril, on to the Plains of the Lost and toward Weird Henge.
The quest is the same except for using Fawrkin instead of Farflame.
Destruction of the Ice Crown will take place around the end of day fifteen.

Method Three: Lake Mirrow

As the previous two methods except you can ignore both Fawkrin and Farflame and pick up the Ice Crown. Bringing it Southwest from the Tower you can destroy it in Lake Mirrow at about the end of day fifteen.
This can sometime get tricky as there are usually a lot of Doomdark’s armies to meet you on the return journey.

Method Four: Lorgrim the Wise

The same as methods one and two except from the Tower of Doom we wish to head Easterly over to the Plains of Rathrorn, keeping north of the Downs and Plains of Lorgrim. Drop Southeasterly toward the Frozen Wastes. Passing through the Frozen Wastes at the Entering at the Lith of Fadrath. At the North most point you will find the Tower of Lorgrim and Lorgrim the Wise.
He will destroy the Ice Crown at about the end of day fourteen.
This is probably easier than Method Three because there are less of Doomdark’s armies to deal with.