Will,
What wonderful memories, and paintings to be treasured. Both photos will make excellent resources - go ahead and do them both!
I probably favor the selection and cropping that Mike has suggested. There are a couple of particular challenges that come to mind as I consider them.
First, with regard to composition: the square (Have you seen this thread on square compositions?
http://forum.portraitartist.com/show...&threadid=1221) is intriguing to me. Should you elect this compostion, however, I feel that the upper right quadrant calls out for some balance. A couple of solutions come to mind. Have you seen Karin Wells's fantastic work, showing the name of the person behind the figure? (Karin, hope you don't mind...) Here's an example, but do look at all her work:
http://www.portraitartist.com/wells/butterworth.htm. Karin uses this convention in an incredibly masterful way for compositional balancing. On the other hand, something as simple as placing your signature in the upper right may do the trick. (I am, BTW, passsionate about how important the signature placement is...as is everything else you place on your canvas, it becomes part of the design, so it pays to consider it carefully!)
Second, you have a lot of challenge with regard to values. Try holding your photo right up against a strong light to see whether you can "tease" out any additional values in the shadows.
Last, the photos present a color temperature problem. They contain no cool colors to counterbalance the powerful warms created by this extremely warm light source. Finding subtle places to place cools in the shadows may create some visual relief.
Best wishes,