Absolutely beautiful work. Your sisters are going to love them.
The stretched wire for hanging paintings is a classic way and great for larger framed work. My only objection to that method is that the portrait tends to lean out from the wall at the top a little.
Most of our framed portrait work is done in typical photo sizes (8x10, 11X14 or some variations near those sizes). And, most when cut in BB ply or similar, are rather light weight as we don't put our work under glass. A simple sawtooth hanger is most often more than enough and only requires a small brad nail in the wall to hang on. This method keeps the work flat against the wall for best viewing (IMHO).
The swivel tabs to hold you work in the frame are great, but you must make the rabbet depth to match the thickness of the panel. I happent to use framing pins to hold the work in the frame so I make my rabbets deeper than the panel thickness. And, they are a lot easier and quicker to shoot in with the stapler like device.