How should I treat these people?

My wife and I had what I thought was a good relationship with her step-mother and her husband. (My wife's dad died 15 yrs ago and SM remarried) We had them over for meals on holidays, birthdays, anniversary. Visited them in the hospital, took them meals when they were ill and helped with other things. Bottom line is they were never reluctant to call us♠ for help with anything.

My wife died last year not unexpectedly but a little sooner than we thought. I called her SM the day she died to let her know. Her obit was in the local paper for 3 days before the visitation or funeral. With funeral details, arranging to pick my family up at 2 airports and put them up in my home and a local hotel I was busy the next 3 days. I didn't hear from her SM. That was OK not really anything they could do and I would rather not have talked about it. I was a little surprised when they did not come to the funeral home. I understand not wanting to come to a visitation. In fact I had written permission from my wife to miss her's. Not coming to her memorial service I thought was wrong. It was a celebration of the life of an incredible woman but even that I could understand. They sent no flowers, no contributions to a charity we put in the obit in lieu of flowers. I never received a card a phone call or anything that would indicate they cared. They ran into my wife's mother several weeks later and told her they didn't get a paper so they did not know the date and time of the funeral. (Other members of his family were there) i live in a small enough town that I am going to run into them some day. How do I react?