Well, first on the list would be to seperate them when you're already noticing pregnancy signs. For how long have they been together? The buck must not be with the doe when she gives birth, he would impregnate her right again, if he even lets her finish. You'll need to securly seperate them, a 3ft barrier he would never go over normally could be not enough.
A nestbox, lots of hay, more food and privacy is pretty much all a doe needs.
When the time comes check frequently about every 2 hours if possible, to help if something goes wrong, like kits born outside of the nest. You might want to have gloves ready for that or for cleaning up the nestbox if it is necessary. Gather fur from brushing them, might come in handy if she doesn't pull enough.