Definite possibilities! Perhaps a LITTLE twisting of the story, just to make it fit into the ride..but here goes..
You first see Oenegus Laying in his bed, looking rather ill...
"Before I became ill...I had an incredible dream..."
You would enter the next scene which would be his dream, pixies and mythical creatures would frollic in and out of bushes, it would be like a neat little forest glen with a pond and waterfall. This would be the part where our 3 cars (three is a good number) would split up, and go on there own adventures through this 'Dream Land', weaving in and out of thick oaks, encountaring Unicorns, Fairies, Dwarves, and any other Celtic Critters. Each car would have a different mixture of animals. But They would all meet back up at the waterfall and pond...
Oengus's voice "In My dream was an incredibly beautiful woman...She was part swan, and her beauty reflected it.."
Indeed, the woman would be beautiful, Large, swan wings, would wave elegently from her back, the rest of her would be human, With a very pale glowing skin, and golden flowing hair.
You would turn from her, and come back from the dream, Oengus would be back on his bed,
"I know shes out there...You must find her...I know she will be the one who can heal me!"
The cars go off, starting in a forest, the three cars would go on three very different tracks.
1. A cave
2. Ocean Side Cliffs
3. Old Ruins (of something or another, some sort of temple or ritual place)
In all three, little fairies (fiber optics) would help lead you through them
Either way, all three cars would end up at a castle, which the would, of course, enter, and go through some halls, despite the shouting of the guards. They would find the room where the swan lady is..
"You must be friends of Oengus...You must bring me to him...But we must get there quickly!"
The little pixies that brought you here would pipe up,
"We can help!"
"We'll just use some magic!"
They would spin around, in a dazzling display of bright colors, the entire room would fade away to darkness, except for tiny lights (think the end of the Imagination ride) and then, a bright light would flash, leaving the riders temporarily "blinded" (like in Posedins Fury) and the cars would move foward into the scene where the swan lady (Who is flying, touches Oengus, healing him...
and causing him to sprout big swan wings as well...
"Come fly with me..." she would say, and your car would turn, and seem to fly upwards, as if flying with them, up through a window and into the stars, then the stars would fade away, and you'd be in the unloading area (think Imagination again)...
I think it sounds fun