I know it's been a while since you posted your question, but I hate to see queries go unanswered - so here's what I can tell you about Lego WeDo, Scratch, and Raspberry Pi:
Firstly, you specifically mention using Scratch 2.0. So far as I understand, Scratch 2.0 has been built using Adobe Flash, and therefore requires the Adobe Flash Player in order to work. The Adobe Flash player is not (and I understand will not become) available for the Raspberry Pi, and so Scratch 2.0 cannot be used on the Pi. Having said that, it seems that the Lego WeDo kit itself does not currently work with Scratch 2.0, although the MIT Scratch team have said they have plans to support it in the future - see their statement here: http://wiki.scratch.mit.edu/wiki/LEGO_E ... botics_Kit
The previous, non-Flash, version of Scratch (1.4) comes bundled with the Raspbian distribution, and nowadays Scratch 1.4 works really nicely on the Pi, thanks to lots of clever development work by people at the Foundation and elsewhere. I can confirm from personal experience that the LeGo WeDo kit works very nicely, out of the box, with Raspbian Scratch 1.4 on a Raspberry Pi. No additional software required! Just plug the WeDo USB module into the Pi, start up Scratch, and off you go! See the above link for some details of using the WeDo with Scratch 1.4.
It's also possible to use Python on a Raspberry Pi to interact with the Lego WeDo kit. For this, you will need to install some Python libraries, but the process has been nicely documented here: http://zdome.net/wiki/index.php/Install ... on_Support
, and the actual Python WeDo library is on Github: https://github.com/itdaniher/WeDoMore
. There is some simple example code for using the WeDo kit with both Scratch and Python here: http://www.ieee-oregon.org/live/attachm ... istmas.pdf
I hope that helps?