As far as I know, there's no family pack for Logic Studio.
I had the same question some months ago- installing Logic Studio in both my desktop and MacBook Pro... so I called Apple. According to them, you can install it in up to 2 computers, as long as one is a desktop, and the other one is a portable, both belonging to the same person, and without running Logic in both computers simultaneously.
So NO: you shouldn't install it in two portable computers... though I don't know if there's a way for them to check if one is indeed a desktop (MacPro, iMac or mini), and the other a portable (macbook, macbookpro).
But one question arises: why would you want to install it in two portable computers? do you use both for personal use? (maybe it's none of my business- I just thought it's odd)