Which rating would be more helpful?

Hello. I'm a 700 hour commercial/single-engine land/instrument pilot.
I'm also 39 years old. I would like to fly a bit
'semi-professionally'; i.e. part-time right-seat for a corporate gig,
ferry jobs etc. I have no illusions about flying for Delta. My wife
and I are expecting another child in a few months, and I know that,
after she's born, I won't be able to do much flying (I think I'll
still be able to get in 50-60 hours a year). Basically, I have time
and money to get one of two ratings before she's born...I can do my
commercial multi, or I can do my CFI. I probably can't do both. And I
would like the opinions of some of the professional pilots out there
about which rating/certificate would help me get into a gig that would
let me fly a bit 'semi-pro'. I have some good connections with some
corporate/charter types, and I have one guy who said he could probably
get me a couple dozen hours a year sitting in the right seat of a King
Air, but no promises. I tend to think that the multi would be the
better investment. I'd like to teach, but in my area we seem to have a
surplus of CFIs, so I doubt I could get on with any of the schools in
the near future. I've gotten various opinions from the full-time
pilots I know. A 135 charter pilot buddy thought I should go for the
CFI, but a friend flying for ASA thought the multi would be much
better. So...any ideas which way I should go?

Thanks in advance