Wow, your daughters are adult, my daughters are 7 and 2,5 yo.
As for HL, if I were you I just skip the whole stuff. Half-life was good, but it is old by now. There are at least two fresh and great looking shooters at the moment (Doom 3, HL2). As for Blue Shift, Opp Force, Team Fortress - theese are multiplayer only addons to Halflife, nothing special imo.
You can puke that's ok (I have a flue <img src="/ubbthreads/images/graemlins/alien.gif" alt="" />), but no turning green no, please, no. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
