Looking for advice (mentor?)

I am going to be working part-time with a non-profit organization, creating their new site using Drupal, and this is only my second paid web development job I have ever done. I have some web experience, I have set up test cms's, gallery and gallery2 site for myself and have done some work with CSS. I've already created a test drupal site for this particular non-profit organization, have tested tons of modules and themes, and I think it will work for them and I think I am comfortable using Drupal.

I would like to ask someone advice about what hourly rate to charge? Or what flat fee rate (for phase 1 of their website) I should charge. There is also the option of charging a much larger amount but then donating my wages back to them and then using the tax receipt to get a tax refund (they are registered as a charity so they said they said I can do this if I want). I need to know stuff like 1) how much is reasonable to charge for a basic Drupal site with some basic functionality (I have no idea), 2) how much is reasonable to charge for creating a new theme from scratch or modifying an old one (no graphic design, except for maybe creating a basic header). I need to come up with some numbers for them. I'm thinking of going with a flat rate because I think they want to know what they are paying first...and I can't really predict how many hours it will take me.

If you want to post to this forum that's fine, but otherwise maybe just chat over email or something would be helpful. I'm also interested in making some contacts as there may be some contract work others can do for this site.