I always take mine to between 200* and 205* and they are perfect. The bone slides out like it was greased with butter and the meat just falls apart.
If it's only having to wait a couple of hours then you can either put it in a pan covered tightly with foil at very low heat in the oven, no problem. You could also put it into something like a crock pot on low to keep it warm for a couple of hours.
I would place a pan under the butt or smoke it inside of a disposable pan so you can catch the juices. Separate the fat by placing the juices in the fridge and once it gets cold the fat will solidify and can be scooped off leaving you with some really tasty juices. These juices can be added back in right before you serve it in case it dries out a little during the holding time.
I have used both of these methods successfully on several occasions.