Hey hi, I was using Xsitepro once. Good software... not flexible but was simple and did the job. Sorry to know that they went out of business. Now, with respect to your website, here are some facts that i collected from my initial analysis.
Total HTML pages - 96
Total HTML content pages excluding tag/category pages - 76
Total PDF files - 60
Total 404s - 5 (All were links related to PDF)
Total images - 138
Total pages indexed in Google - 146
Total html files indexed in Google - 74
Total PHP files indexed in Google - 1
Total PDF files indexed in Google - 70
Total links to external websites - Atleast 183
I wanted to share these results with you, as i read that you were thinking that there are only 37 pages in your website. Irrespective of whom you award this project to, I wanted you know these facts. Because i own some websites too and i know how hard it is rank in Google. I dont want this migration to affect your rankings.
Now, can i guarantee that your rankings will not be affected? To be honest, no i cant and nobody can. But, I can take meticulous care not to disturb the current URL formats and internal linking, so that there will be very minimal chances for negative impact. And also, your visitor bookmarking wont be affected.
Regarding downtime, we can setup this wordpress site under different folder in your domain and once you test it and everything is good to go,we can just move the entire wordpress site to the main root domain folder, so that its seemless. Let me know