Is it necessary to change one's sitting place for Duha prayer and reading Qur'an to preserve the reward if the father is watching television in the same place?

If your remaining in your prayer area does not lead to hearing or seeing something forbidden on television, and it does not cause you distraction or preoccupation from dhikr (remembrance of Allah), then you may remain. However, if any of that occurs, then get up and sit in another place where you can devote yourself to dhikr. You may still be rewarded as if you had remained in your prayer area, as long as you moved due to a valid excuse.