Don't know what the tankage is on a C42, but a watermaker might make up any shortage. Since you want extra cabins and only plan to cruise for a few years and not push the boat too much, what about a used charter boat of appropriate size? Would be a lower cost, but would need more upgrading, but probably cheaper overall.
Heading back to Lake Ontario for this summer. Relatively few stops along the way from Grenada. Martinique, Guadeloupe, St. Martin (must have something to do with the French food), then Bermuda, New England and up the Hudson/Erie Canal. We were going to go via Newfoundland and Labrador but June remembered that one of the kids is getting married this summer - details, details!