HELP PLEASE!!!!

I just got 5D and I really like it compare to my 50D. It comes with 24-105 and I like it better on my camera than the 24-70 although 2.8 is a plus, but then since I decided to keep the 24-105 and sell my 24-70, I have 2 options to buy :
50 1.4
or 85 1.8

Mainly the purpose for this prime will be for taking pics of my kids and job related photography (kids and babies) indoor, studio lighting or just available lighting.

If you have only afford 1 lens at this time, which one you should get first ?

I know this thread is like so many, but I couldn't really find the answer which satisfied me.

Thanks

Spend a day with your 24-105 "locked" at 50mm. Then spend another day shooting only at 85mm. Which do YOU prefer?

Yes, indeed. You already have a 50 and an 85 - ok, slower ones. Both the 50/1.4 and 85/1.8 are great choices IF the focal length is right for you.