His card expires - but his residency does not expire.

Legally he's supposed to keep his card current and on his person, but realistically nobody is going to give a hoot if you get married while a replacement card is pending.

Remember, the card itself is only physical proof that he's a legal resident - that's all it is. Get married, have fun and deal with it later once you're back from cloud nine

Here you go: http://www.uscis.gov/green-card/afte...new-green-card

Good luck!