Chip, first of all, cool shots.
No, don't need to be brand new photos. Photos you've already taken will work.
No picky rules here, this is all for fun and learning, hopefully in that order.
Please let me stress again, there are no "rules" here, but when I mentioned silhouette, I was thinking that the subject of our photos would be featureless (an outline colored in with black magic marker). In your first photo, mentally place your son right on the edge of that cliff
, then remove the mountains right in front of him as they will detract from his distinct outline, then have him watching the setting or rising sun so wrt the camera he's backlit, then make sure you don't use flash and you do expose for the sky. Voila, a sharp black silhouette of your son against a bright background.
Of course, easier said than done (especially the part about dad placing son on edge of cliff), but that's the gist of it.
Same idea with the guide....put him on the crest of a ridgeline with nothing but clouds and/or sky behind him.
If you want to see how a pro does it, check out Tim Seaver's avatar. If you want to see how a hack does it, stay tuned for my entry.