Implementing site todo lists and logs

I'm struggling with figuring out how to set up the wiki to support site logs and todo lists, two of the primary features this thing is intended to help with. Part of the problem is that it's not easy to google for this kind of "meta" information; instead, the results seem to be actual todo lists rather than howto's on the subject.

What is it that we want to do?

• user-editable comments

This is implicit in the use of a wiki

• TODO list should reflect what needs to happen on the next site visit

This could be a list of tasks, sensors needing replacement or attention, measurements that need to be made, etc. Once done, it is hoped/intended that the list be updated, so that it ALWAYS reflects the current situation. Of course, this is probably not going to happen in many cases, but it's still the goal.

• site logs should be time-stamped comments on what went on or was found at the site

The intention is to have an entry representing each visit to a site, with the newest at top, older below. For a start, this probably can just be done by editing the entire site-log -- but at some risk of a user accidentally screwing up the whole thing... Not sure how to protect against that, other than maintain backups and be able to redeploy them.