Hi B Relan,
I would get a few more test holes. They are cheap compared to the total cost you are thinking about investing in the site. Try to get them strategically located within the area to be innundated by water so you can get an overall indication of suitability, and hopefully locate any problem areas if they do exist. I would also investigate what appears to be the worst-looking sand or gravel area with the backhoe just to see exactly what it amounts to and whether it is a closed pocket. I believe your optimism is well founded. Locate your site on a soil survey and read up on the soil descriptions for all of the soils involved, paying particular attention to the subsoil classifications. Good luck and keep us posted.
