need advice on best way to upgrade from 2.6 to 3.1

I have agreed to help a friend upgrade/move his site from 2.6 to 3.1, giving it a new fresh custom made theme. It is an old site (upgraded from 2.2 I think) and the database has one or two extra tables created by plugins (random quote functionality) where one table is an orphan from a plugin no longer in use. There are not many posts, I think less than 50, but they are pretty long articles. And there are a lot of links in different categories and maybe 5 pages linking to quite a few self-hosted pdf-files, some of which are pretty large.

I need advice on the best route to move/upgrade this site. As far as I can see there are 3 main options of how to do this upgrade.

1. – Go the “traditional” route with saving a backup SQL-dump, put up a temporary static page, and install/upgrade version 3.1 in place on the live site. Install the new theme, check everything is working, and remove the static placeholder.
   I like this solution the least, because I am afraid it will leave a lot of legacy unused information lying around in the database and I would for some reason like a clean slate to start from. And I am not comfortable with messing around on a live site, even if I have backups.
2. – Do an SQL-dump of the site and import it into a local wordpress install where I do the upgrades incrementally, 2.6 -> 2.8 -> 3.0 -> 3.1. Check in between that everything works as expected, do an SQL-dump of THAT and import into a new fresh install on the server.
   I am more comfortable with working on a local copy, but I would still have the issue of extra/legacy information in the database, unless I clean it out manually.
3. – Go the route with exporting and importing the blog with WXR-files to/from the local installation. This way I will only get the actual contents of the site, without the extra tables created by the plugins. Since the new theme has a custom post type, that information will have to be reentered anyway and I can live with that. The drawback with this is of course the size of the WXR-files. They might have to be split.
   I like the idea with importing only the content into a fresh, clean, new install. But I am not familiar with the reliability of the wordpress exporter/importer. I COULD even do a WXR-import to the local wordpress install and once upgraded import an SQL-dump of THAT into the live site.

I would of course disable all the plugins before starting, and install the latest versions of them after all has been upgraded.

In the new theme, I created a custom post type for the random quote so the plugin and its table is no longer necessary. That information would be reentered anyway. But since the site is quite old, I don’t know how the upgrade will handle the categories associated with links and posts with the taxonomy features of today. Do I need to re-connect them after upgrade or will their association migrate as well? And what will happen with the uploads?

I would like to know the benefits and drawbacks of these options. Maybe I am just making it too complicated for myself with all this, and the “traditional” route is quite enough. What would you do?