During the lockdown, the government has advised citizens not to visit friends and family if they do not live with us as part of social distancing measures enforced. However, I am concerned about my mother who does not reside with me and my father has passed away. I feel she is in a vulnerable group and may get anxiety from time to time. Every once in a while, she would like me to visit her. Is it permissible to travel to visit her? I am not too concerned with the other people that live with her such as my siblings. If I can visit, how much precaution should I take. Can I take other members of my household to visit her such as my children, wife etc.

You should try to keep in touch remotely and not visit since it may endanger her life. This decision is difficult but ulema have instructed us to abide by law of the land as much as possible. If she is in real need and you must see her to save her life for eg then there maybe an exception
Ofcourse if you live in that house too with her it’s ok according to the law.