If you are definitely going for commercial firms I'd recommend Company law. Company law is probably as important as every other area of law combined at city firms. You do learn it on the LPC but not in as much detail and I find knowing Company law better than people who didn't study it useful.
That said, it is fine if you don't do it too. I'm not sure I'd describe Family as "easy" in comparison to other subjects. Most of it isn't that difficult conceptually but there are quite a lot of cases. Company law can be tricky in places but generally I don't think its too bad and it is certainly comparable with subjects like Equity or Commercial law or Conflict of laws and so on. Company law is basically just knowing your way around the Companies Act 2006, and if you can do that you are away - its a very statutory subject, but then again so is Family law. Some people have trouble adjusting to statutory subjects - with subjects like Criminal/Contract, much like at school, there is a fair bit of lee-way and you can get away with being sort of in the right area and referring to cases sort of accurately. With Company, you MUST read the relevant section of the CA and have it with you and refer to it in the exam. Vague recollections of the sections simply won't do, you've got to look at the precise words used. This is a skill that isn't used so much at uni in most subjects, but is essential in practice. Once you can do that, its a normal third year subject IMO. Family is very statutory too, but the statutes tend to be a little more vague and rely on case-law to flesh them out.