Man, goirish, you sure ask a damn lot of questions!!

They're good questions though. I always plan to try and do too much myself and I don't see anything wrong with that. I think the important thing to keep in mind when traveling in Latin America is that they don't operate on the same conception of time as you do and as with most trips things will not always run on a tight schedule. Stay flexible, TRY and fit in as much as you can but if you can't, don't sweat. If you are like the rest of us, you will probably end up wanting to come back and whatever you miss on the first trip you can always try to get in on follow-up trips.
With those general comments in mind, I would say that, while those other locations can be done as overnight trips (there is even a LONG one day tour package to Tabacon), it is best to allow at least two nights at each place if not more. That way you get in at least one full day. The day trips at each place generally start early and end late enough that you probably won't want to start a 3-4+ hour drive to another place. So 2 nights are good as a minimum.
Another thing is that unless you hire your own driver or rent a car transportation between Tabacon and Quepos is a bit more difficult to arrange or costly. It is a long drive, probably going through San Ramon which is only 30-45 minutes outside of San Jose. Most bus routes go to and from the capital anyway. You might consider returning to SJ for a night in between but it certainly can be done the way you describe it. Also if you plan to arrange for a travel companion, keep in mind what is great for an hour or two may become tiresome for 24/2. Returning to SJ gives you an opportunity to more easily make new arrangements if it becomes necessary.
You can arrange WW raft trips at any of the locations you mentioned but I recommend you do it out of San Jose. It makes for a good way to get out of the city for the day and there is nothing like a session at the NF to work out the kinks after a day of rafting (and you don't have to pay your driver if you go that route while you are rafting). If you plan on trying a canopy tour, I definitely suggest you book it at either Quepos or Tabacon (you can also do it en route to Quepos at either Iguana Park or Chiclet's)
So here are my recommendations: Sat and Sun in SJ with a raft tour one day, Monday drive to Tabacon (its a gorgeous drive, so take your time), return to SJ on Wednesday, maybe check out the Tierra Tico night at the Mirador Ram Luna, first thing Thursday head by bus to JACO (its not as nice as Quepos, but not quite as far and has more nightlife), do a canopy tour on Friday morning and hang out at the beach some more before returning to SJ late Friday (maybe catch the Oil Show at the Park Hotel that night), heavy debauchery all day Saturday or another tour and return home on Sunday. What do the rest of you guys think?