Hej again,
we use serial-usb converters all the time. You should just aware that from the broad range of converters existing in the market, there are a few that will not work. Brands including the FTDI chipset like ATEN or KEYSPAN work fine both for PC and MAC.
In order to get the discount you just need to show us that you are a student/group of students. We are not aiming to make money with this project, therefore if you don't get support from your teacher you shouldn't worry too much.
About making your own workshop, we will encourage it and support you entirely from here. All our examples are open and published on the net. And we will be happy to help you with whatever questions you come out (to a certain extent).
Finally, if you feel like you want to develop your own boards, because of price, you are welcome to do so. I would recommend you to start checking out Dave Mellis' explanation on the smallest Arduino system at:
and also Tom Igoe's standalone Arduino board on a prototyping board, available at:
/David
PS. I don't like 8051 either 