Use the Safety Lead Time on the Planning Data tab of the Inventory Part (IEE) or the Inventory Part Planning Data page (Aurena).

Safety Lead Time:
Time defined by days to protect against unpredictable variations in the supply chain and its associate logistics. When it is used by MRP, PMRP, MS or Project MS and Next Level Demand, the required date of an order will be placed before its real need date. It offsets the required date by this time so that it will plan order release and completion for earlier dates than it would otherwise. Syn: safety time. Value can be updated manually or else it can be updated via Modify Safety Lead Time dialog box. Safety lead time is not used for parts with Planning method B, C, K, P, O, T and H. Note that the safety lead time will be considered in Cumulative Lead Time Calcualtion.

@Dsquared As suggested by Matt, the Safety Lead Time is a good idea to create a buffer between when the purchased parts as planned to be received to stock, and when they are required on the shop order.

Another option might be to set a Queue Time on the work center of the first operation. This will give an earlier start date of the shop order creating a buffer between the shop order start date and the actual start date of the first operation on the order.

Thank you - these are both good options.  I am going to test them both.