This is really tricky. I tried it last year, inside, my DD blowing out candles. Of course if I metered for her face, the candles were over-exposed. So I guess you have to compromise a little. I'm not sure of a better way. This year I was going to try metering for her face then to compensate for the candles, under-expose by -0.7-1 stop.
You are confusing yourself with what metering mode is for. Changing your metering mode will not affect your focus. You can read here about metering modes
http://www.dpreview.com/learn/?/key=metering
Check out the 2 page thread that Keagsmommy posted for help with your focus