It's not a terrible thing that they are using pacifiers. Begin the weaning process by having them use them only at home, never outside the house. Then gradually limit some of the situations inside the home as well. But there's no need to rush, particularly if you limit the use outside the home.
I know on Supernanny she discusses it with them, telling them that they are big kids now and that the "pacifier fairies" need to take them away to give them to the little babies who need them......she has them go round the house and gather them all up, then put them somewhere for the pacifier fairy to come and collect them overnight - in the morning they go and find that the fairy has left them presents in exchange for the pacifiers.
Don't know if that would work for you or not......but it's worth a thought.