Bridal Shower Etiquette

This past week I held a Bridal Shower for my sister. She and her fiance have been dating seriously for 4 years and were planning to wed in March. Due to downsizing at his job (that he held for the entire time they were dating), they`ve decided they must postpone the date until he is secure in a new job.

Her question to me was should she contact the shower guests and offer the gifts she received back to them or should she send thank-you`s with an explanation of the unforseen postponement and save the gifts until they do actually wed?

Your help would be most appreciated.