I just think everyone is different. I definitely dont think its fair to characterize the decision of continuing to stay on course with school as selfish. It may make his mother happier to see him begin law school and pursue his aspirations. She may feel guilty if he does decide not to go. He could regret the decision, become depressed, and then feel terrible guilt for having feelings of regret. I think the ideal scenario of not going to school to spend quality time with family may not reflect reality.
I just don't think it is reasonable to say do this or do that. The right answer will be different for different people.
You should definitely defer. Law school will still be there, your mom may not. One of my biggest regrets is not getting the chance to say the things to my father that I would have liked before he died.
Even if you look at it from a selfish perspective, you will be harming yourself in the long run by not doing your absolute best while in law school. You can't go back in time once it's over and re-do law school, and you can't re-live the missed opportunities with your mom.
Of course he will ultimately make his own decision. If he is going to base a life-altering decision on a few posts from on an internet discussion board, then he is probably not in a position to make any major choices.
The "reality" is that law school is not life. The world does not end when you take a year off..even though it may feel like it to those of us who have only known life as a student. If you look at any decent book on law school, it will tell you in black and white that if you are experiencing a crisis of any kind, you should get it over with before going to law school.
From personal experience, I remember how horrible it was to have to go through losing a parent, and I was only working at the time. I had to take an entire week off, and even then I wasn't anywhere close to 100%.
How horrible do you think both he and his mom would feel if he did poorly in school, or worse, quit early, because he wasn't able to focus on his studies. Whether your motive is concern for your mother, or self-interest (which, is not necessarily a bad thing), it benefits you to defer.
But, this is just one opinion.