Changes to Trip--How to "cancel" return flight

The family and I are going to the midwest to visit my father-in-law. Now I have just heard my grandmother is not doing well, and was thinking about going for a quick visit (she also lives in the midwest). We have RT airline tickets with Delta--on the same reservation #. What I would like to do is to not take the return trip, and just arrange to go see my GM on the same day as the rest of the family flies back home. However, I'm concerned it will be frowned upon by Delta and my family will be hasseled on their return trip. Any suggestions/comments? I have not contacted Delta yet about this all.

Delta will change your return flight, but for a fee.

It sounds as though you want to completely cancel your return trip, not reschedule it. If so, just call Delta, as a courtesy, shortly before the return flight and cancel, making it clear that it's only your reservation being canceled. Delta's revenue police are out to get those who book cheap round-trip tickets with no intent of flying round trip. That doesn't apply to you, so don't worry about it. You won't have a problem.

One potential issue is seat assignments. For example, if you are scheduled to sit four across and your seat is somewhere in the middle two seats of the four, the other three will be split up if you simply cancel. Check your seat assignments and call to rearrange, if necessary. Do it now so you won't have a problem with losing seats if someone later tries to rearrange when there is a waiting list for seats.

And as susgar states, if you simply want to reschedule your return, call and do it now. The fee is $100, plus any amount related to an increase in the fare since you booked your tickets.