ASRS 1688615

During taxi, as I take my position as B [flight attendant], for the safety demo I could hear an electronic device rows away. As I approached I noticed two children in seats 10 A and C were watching their iPad without headphones. I informed the mom sitting in 10C they are required to wear headphones or it must be muted. She stated that this is their 3rd flight and no one has told them this before. I apologized that it was missed on a previous flight. I continued the safety demo and she said she would like to see it in writing. I told her I would need to get back to her as I am in the middle of the safety demo. A neighboring passenger showed it to her in the in flight magazine. After the demo, I secured the galley and it was time for takeoff. I was unable to go back to her at that time. After takeoff I checked the entertainment kit and no headphones were in the kit. Shortly after the seatbelt sign came off a passenger came to the back galley and handed me a paper with her contact info and told me she is seated in 11B is a witness to the exchange between the passenger and I and she wanted to make sure I was covered because she heard the passenger telling her son they "cannot use the iPad because the flight attendant yelled at her and said they couldn't use it." Also the other flight attendant said a passenger in front of 10C offered her an extra pair of headphones she had and the passenger refused and said her son was autistic and required special headphones. The work group could be consistent on their flights informing passengers about the headphone requirements. If there had been consistency this situation could've possibly been avoided as the passenger could have been prepared.