It sounds interesting... but... this board isn't precisely the best candidate for an "introduction to soldering"
I assembled my board with a soldering station, but the right way to do it would be with a reflow oven.
To do the soldering with reflow oven there would be needed stencils, as this would be for a small quantity kapton stencils would be ok (instead of the expensive metal ones).
To assemble my board I don't remember exactly but I would say I may have used about 15 hours. Then, of course, you have to troubleshoot the board. Nobody should really expect to have the board fully functioning at the first time... I may have also used 10 hours trying to find my mistakes.
To test a board like this, a multimeter is essential, but probably insufficient, an oscilloscope would also be needed in most cases.
I know I sound pessimistic, but what I mean to say is that in a workshop there wouldn't be enough time to assemble them by hand and have functional boards by the end of the day. Placing the main ICs is one thing, but then there are still 200 components to be mounted, is a repetitive task and you have to do it carefully.
Getting all the components shouldn't be a problem, if you get them on farnell/mouser/digikey they are very quick. If you want to get a better price at other dealers you may have to wait a bit more.
And for the tools, this is what in my opinion is needed, in the workshop or for anyone who whants to build it at home:
Soldering station (solder iron + hot air)
Solder wire, small diameter (0.5mm)
Solder wick / solder sucker (it's better to have a good quality solder wick)
Solder flux (a solder flux pen is a good option)
Isopropyl alcohol (to clean the mess)
Reflow oven / stencils (not a requisite but it would speed up the process)
Multimeter / Oscilloscope (to test everything)
Linux PC with arm cross-compilling tools
ARM-USB-OCD JTAG or similar tool (I think that xobs and bunnie doesn't use JTAG)
3.3V FTDI cable, BusPirate or similar tool
As I say... I may be a bit pessimistic about the feasibility to have completed and functional boards in an event like this (but I have never been in a practical workshop like the one you are proposing! So I don't really know how this would go). But lets see how many people would be interested and also if there are people with more experience in this matters that can give us their opinion.