I want to field a team, but some people want to do the 5k and others want to do the 10k, and others want to walk. Is this OK?

Yes, but be aware that your team will NOT be eligible to compete for the team awards unless there are at least five people running in the same category/distance. To be eligible for team awards, at least five members must be registered under the same race category. Teams are eligible to win under both race categories (10K and 5K) only if at least five members are registered under both race categories. If your team does not wish to compete for awards you still must have five team members but you are free to have these members in any or all race categories.