Years ago, I wrote the LSAT in September of my third year of undergrad. It was fine. I didn't have to worry about it anytime close to when I was applying. The LSAT should be written as early as possible as long as you are well-prepared and have been consistently scoring well on the practice tests. Too many people leave it til the last minute and that's a mistake. You should have a competitive valid score in hand prior to applying so you know where you are a competitive candidate.
Demonstrated interest through ECs will go a lot further in applications/interviews than a grade, so I wouldn't worry too much about it.
Something not entirely relevant but anecdotal: I had a class where my grade was lower than I anticipated, so I went to see the prof and review my exam. In reviewing it they found that they incorrectly marked a multiple choice question (for law...I know...) and with the correction it bumped me up a grade. Also in reviewing it, they found that my fact pattern/essay response was among the top of the class, but I just bombed the MC (which is why multiple choice should not be a thing in law school). They immediately corrected the grade/my transcript and offered to write me a reference letter explaining why my grade, though good, wasn't entirely representative of my knowledge in the course - just providing more context to the grade. Does your prof know about your interest/EC activity in family law? Do you have a rapport with them? You could always request a letter if you're worried about it. It wouldn't hurt to approach them and even say "I'm worried about this grade, I want to go into family law, I'm applying for articling positions - is there anything you can suggest I do going forward?" This could either open the door to a) a reference letter or b) their recommendations for courses, ECs, research help, a referral to someone that might be looking for a student.