Most all good advice has been said. I say bite the bullet and try to cope with the large group all at once, but definitely consider conscripting one of them as a DM aid.
There are only two things I didn't see already said:
1. Plot-related teams! Have groups of 2-4 characters in the game world that share a background, motives, family, clan, romance, or whatever. For example, I had three players playing a noble, his bodyguard, and his tutor. This way they will act together naturally if they're playing in-character. Combine this with some of the other advice about insisting people pair up or whatever you like.
2. Watch out for out-of-game conversations. I don't know about how focused your group is, but its hard to imagine any group of 10 gamers getting together and not wasting at least half the night talking about the latest video game, movie, or whatever. While this is fun, it defeats the purpose of the get-together: the game! State up-front that you'll have to interrupt such discussions if they get out of hand.
Good luck!