First, I just want to say, if they're only using the pacifier for sleep, don't stress about it too much. I've spoken with a pediatric dentist and two pediatricians about it, and none of them was concerned when my 3 year old was still using the pacifier to get to sleep - in fact, they expressed more concern that if you take it away too abruptly, he could substitute with thumb-sucking, which is a much harder habit to break (you can't take away their thumbs, after all.) There's no impact on their teeth until the permanants start to come in, and as long as it's just for sleep, it's not interfering with their verbal or social development. I think we feel a lot of unnecessary guilt about the pacifier - it's a useful tool for self-soothing, and they're not going to go to kindergarten with pacifiers hanging out of their mouths.
That said, when my son was 3-1/2, he really really wanted a kick scooter, and we saw it as an opportunity to make a trade. (He had been using the pacifiers only for sleep since he was 18 mos old.) The timing came around Christmas, so we told him that Santa would love to bring him a scooter, but he could only bring the scooter to big boys who didn't use pacifiers any more. We made sure to tell him that if he wasn't ready to give up the pacifier, that was totally OK and there would be other chances to get the scooter. (The Pacifier Fairy or Easter Bunny or any other magical gift-giver works just as well.) The key here is giving them control of the situation - we talked about it for several months ahead of time, and made a specific plan about how we would leave the pacifiers for Santa on Christmas Eve, right next to the cookies. Until the moment of truth, I really wasn't sure which way he was going to go, he was very attached to the pacifiers. But he did it, all on his own - and he got his scooter! The next two weeks were a little rough, and he needed a lot more attention at nap time and bed time, mostly just wanting us to stay with him until he fell asleep. He occasionally does a little bit of finger sucking, but so far no big deal - and he goes to sleep just fine on his own now.
I suppose the real moment of truth will come when his brother is born this summer and he sees him with the pacifier - but we're really hoping since he got to CHOOSE to give it up because he's a BIG BOY, that he won't feel much conflict.
Good luck!