Do what you can to get their room ready for them before any other room. Since it is a new construction you may be able to get the builder to paint that (and your other rooms) the color you want (make sure they use eggshell and not that builders flat paint or you will be painting the house yourself very soon!).
Make the boys part of the construction process as well. Especially your 3 year old. If you show them the property at various stages of construction, show them where their room will be and play stuff they will be more comfortable when put into the new space.
Have the boys stay with family for a couple of days during the move-in process so that you can set up their beds and personal items in the room - then they will have a comfort zone to go to as well.
Finally - know where you are going to designate their toys and make sure they are out of boxes when they get there so they have something to do while you and family unpack.
We moved into our current home when my daughter was 21 months old. I had the play room all set up (including gates to keep her in) prior to us moving in. She does not even remember our old house now (it is kind of sad!).