Coming back to the U.S. will be a hellfire of customs hassles. I envision one way OUT of the U.S. I think that may be enough stress on people's boats and knees also, even in the late spring/summer.
The larger course idea sounds interesting, but I don't like the idea of running along the U.S. coast and chopping up scuba divers and kayakers. Running from Miami to Ft. Lauderdale or Palm Beach always freaks me out with all the divers, buoys and kayakers out there these days.
One way across the stream is enough for now. If that works out, a round trip would be next, followed by a larger course as per your suggestion. In my life, KISS always works best.