This is what I would do.

So long as you're not leaving anyone alone, I don't see any problem with upgrading. Or if it's not possible to get seats together. I've had this happen before, where I'm traveling with two people and I can't get a seat next to them. I'll take the upgrade in that case.

But I've discussed this with other people who don't think it's cool. They think everyone should sit in the same class. I don't understand where they're coming from, however.