hey edgerulz,
On Monday, I was in the GA line for the entire day (37th in line, so right from the start), and I very politely went up to the three or four groups behind me and asked if it was ok for my girlfriend to come after work. Everyone was very nice (and by the way, if anyone reading this is from those groups, I can't tell you how grateful I am -- thank you so much!), but make sure you are honest and upfront early on. If they see that you are willing to suffer all day in line and don't take a zillion breaks, I'm sure they'll be ok with at least your wife coming in line -- especially if she's pregnant. Getting two others in line could be tough though...but again, just be honest -- maybe even offer to buy them coffee or snacks throughout the day, or try to offer help when you can (ie if it's raining and someone doesn't have an umbrella, etc).
I can tell you this though -- there was a large group of people in front of me who switched on and off all day (maybe 2 or 3 hours each) and when they came back to the line at about 5:30, the people behind me (the same ones I asked) were not happy and actually got a chunk of the group sent to the back (mind you, I think the people that got sent back were not there at all until 5:30, so it was just). However, you certainly could ruffle some feathers if you don't ask first.
Good luck -- enjoy the show!