Because of your deadlines and the fact that others will have to maintain it and those others have limited programming experience, I'd recommend the old unix maxim: make lots of small tools that do one job well.

Make a thing that generates the CSV files. Then make a thing that takes a CSV and makes a graph. Then make a thing that gives users a nice interface that lets them choose which csv to make into graphs. There are many ways you could break it up.

With this approach, if the user interface bit fails for some reason, your successors can fall back on the command line tools. You or your successors can make multiple user interfaces (one gui, one web etc.. etc..) without duplicating the effort of making the data-to-CSV and CSV-to-graph bits. This last point is especially nice if the person making the new user interface isn't you.

--Pileofrogs