I know attorneys and their websites. It is an under served market.
Making separate sites makes each site thinner and confuses things. No. I suggest revamping his site. Get rid of the personal stuff. Get professional. Get him to write long and short version articles- post the long version on his site, and the short version on sites such as Avvo. For attorneys, social media, not twitter or facebook, but participation in the legal sites where people research attorneys and read articles about what they are having problems with is paramount. Complete the profiles and so forth. Also focus on local search. Locale is extremely important for attorneys.
In fact, articles help people to feel better about the attorney and help with search. Empathy is key along with professionalism. Keep in mind that people read these articles to not only understand what is happening to them, but to also feel better about the situation. I have seen both attorney and medical articles that are excellent in that they are informative, factual, thorough, and perform well. The problem is... they scare the hell out of the reader. Do not do this. Give the good news and the possible avenues to take. Stay positive and the attorney will convert like crazy!
People find attorneys differently. Yes search is important. But the various find a lawyer sites are more effective. As well, when someone has a legal problem, they want a professional that knows the industry and the issues associated with the problem. If the attorney is a GP (general practitioner) then they must focus on core areas of business. Nothing loses trust more than a GP that says they do tax issues then to find out they only negotiate tax issues and does not know tax law very well at all. The primary focus of the site is not just to be found, but to be linked in (so to speak) to the attorney research sites, and build trust- serious trust. One factor is to create an online resume on his site. Make it foremost and thorough. Post all the accolades, degrees, certifications, and volunteer work.
Again, never put personal stuff on a professional website. This is especially true for attorneys! TRUST is and CONFIDENCE is what you need the site to convey.
Then worry about traditional SEO. Focus on local search. Fill out the profiles on the attorney sites and his site will perform much better.