Kari - The prep process has changed a lot since I "auditioned" for About.com in 2000, but I'm sure the editors don't expect you to cover everything in just two weeks. They are anxious to see how well you write, understand the tools, organize a Web site, and follow instructions. If you meet their expectations better than your competition, then you will have PLENTY of time to change your organization, add categories, sub-categories, etc. In fact, you will want to make changes as you see what is popular (and what is not).
The cuisine guides have 15 categories because that's all we are allowed now. When I joined, we had 30, so we have re-shuffled the deck a few times to get down to 15. Now, with the re-design the emphasis is on other tools. So, even if I thought I had everything organized the way I liked it, About is continually changing the format to keep up with the times, so we are continually changing the way our sites look.
On another note, you might mention to the editor that vegetarian food is not popular in Scandinavia. He/she might want you to discuss and find a few recipes anyway since all the other "food" sites have vegetarian categories. Maybe an article on why vegetarian food is NOT typically Scandinavian would be interesting.