Simple in theory, but every page must be rebuilt into a new site/platform.
I don't know how many pages are on this site, but I would charge at least $100 per page
I just spent over 250 hours on a wp project I did for an old co-worker. I under bid it by about 100 hours and am still paying the price (doing more work for free)
Have you considered switching the site to something like Wordpress
Wordpress sites use "themes" which include mobile layouts for multiple device types (Phones, tablets, desktops).
The content stays the same regardless which device you use, converting the main Catsailor page to Wordpress wouldn't be that much work since its a pretty simple layout.
