These are some points you could use:
-when did you visit, you should be specific: what time, day, date
-how was the surrounding
-what activities did you do: listen to the old folks' stories. play board games with them, play the guitar for them
-did you have lunch with them? did you have fun? express how you felt: happy, tired/exhausted
-mention that this was a great trip, you hope to visit them again soon as they enjoyed your visit.
If you plan to make a report, don't forget the format :)