I've been whitewater rafting (and inadvertent whitewater canoeing ;) a couple times, and I'd like to get a bunch of friends together to go with me. I'd bring enough people to fill a raft (5 or 6), but the problem is, everyone will have different levels of skill and experience.
What should I consider when choosing which class of rapids we paddle? Are there any rules of thumb for how the ratio of experienced to new whitewater rafters corresponds to the rapid class we can safely manage?
For example, if three people are experienced whitewater rafters and three people have never been before, would class IV rapids be unsafe for the group as a whole?