I've built a number of websites for some non profits. I learned a lot of things the hard way, not a problem for non profits. This is your business, if you don't know what you're doing you need some help setting it up. Setting a bad first impression when advertising is worse than not advertising
You need to figure out the hosting issue, what kind of bandwidth/traffic are you going to pull?
Are you actually doing commerce on the site or is it just a "billboard".
What name or URL are you going to give it, who's going to handle the registering.
What are you going to do to promote the site?
Ironically, the best advertising for web design is word of mouth or looking at the authors of sites that you find appealing. You can find some of this information using Internet Explorers VIEW > SOURCE tabs. You can usually find the author and composing program in the heading.
You might also consider taking a community college course in the subject, if you decide not to DIY then you'll make some contacts.
dave