FWIW, I agree - just leave it alone! I've never heard of an "elite" frequent flyer member bumping someone out of an assigned seat, anyway. I've flown a lot - both as an elite flyer on NWA and on many other airlines as a "regular" passenger. Have often sat in the "elite" section and never been bumped out or seen anyone else bumped out. As far as I know, the only difference in seats (on Continental anyway) is that those "reserved" for elite flyers are in the front of the plane. It's not like they are any bigger/wider.
It's common (and indeed usually necessary) for seat assignments to be changed when the airline changes the type of plane. The farther ahead you book, the more likely it is that the schedule or plane type will change. Sometimes, they change more than once. When changes are made, the airlines do try very hard to keep parties together. However, unless you made the reservation for everyone on the same call/transaction, they have no way to know that you all belong together. I know that is not the OP's situation.
We've been separated on those occasions when one person uses FF miles or when one group/family makes a separate reservation to use a different credit card than we are using. If I am making arrangements and anticipate this could be a problem, I ask them (always, family, LOL) to let me put it all on my CC and then for them to give me a check.
If you happen to pick (or get assigned to) a bulkhead seat right behind the First Class section, you sometimes do get asked to move if that seat is needed for a disabled/handicapped person. That's rare and you usually get a comparable seat nearby and sometimes, a coupon for extra FF miles.
Lots of extra info you didn't ask for. Main point - let it go, quite calling Continental and QUIT WORRYING!!!!
If they gave you those seats, just be quiet and let it happen. 
